Fix all validateLinks issues

[rvedotrc]

Fixes all the issues found by validateLinks (see #21).

❯ ./lint 
validateLinks: ...
error BROKEN-INTERNAL-LINK courses/Foundation/HTML-CSS/README.md:0 Link target does not exist: ./Pre-course/README.md
error BROKEN-INTERNAL-LINK courses/Foundation/HTML-CSS/README.md:0 Link target does not exist: ./Pre-course/README.md
error BROKEN-INTERNAL-LINK courses/Foundation/HTML-CSS/README.md:0 Link target does not exist: ./Pre-course/README.md
error BROKEN-INTERNAL-LINK legacy/career-training/week-3/preparation.md:0 Link target does not exist: ./novoresume-interview.pdf
error BROKEN-INTERNAL-LINK legacy/git/git1/lesson_plan.md:0 Link target does not exist: frequently_asked_questions.md
error BROKEN-INTERNAL-LINK legacy/git/git1/preparation.md:0 Link target does not exist: www.github.com
error BROKEN-INTERNAL-LINK legacy/git/git1/preparation_flipped_classroom.md:0 Link target does not exist: www.github.com
error BROKEN-INTERNAL-LINK legacy/git/git1/review.md:0 Link target does not exist: www.github.com
error BROKEN-INTERNAL-LINK legacy/javascript/homework-projects/projects/currency-converter/currency-converter.md:0 Link target does not exist: /homework-projects/guides/making-your-API-guide.md
error BROKEN-INTERNAL-LINK legacy/javascript/homework-projects/projects/memory-game/memory-game.md:0 Link target does not exist: /homework-projects/guides/making-your-API-guide.md
error BROKEN-INTERNAL-LINK legacy/javascript/homework-projects/projects/movie-app/movie-app.md:0 Link target does not exist: /homework-projects/guides/making-your-API-guide.md
error BROKEN-INTERNAL-LINK legacy/javascript/homework-projects/projects/quiz-app/quiz-app.md:0 Link target does not exist: /homework-projects/guides/making-your-API-guide.md
error BROKEN-INTERNAL-LINK legacy/javascript/homework-projects/projects/recipe-app/recipe-app.md:0 Link target does not exist: /homework-projects/guides/making-your-API-guide.md
error BROKEN-INTERNAL-LINK legacy/javascript/javascript2/README.md:0 Link target does not exist: /homework-projects/readme.md
error BROKEN-INTERNAL-LINK legacy/javascript/javascript2/README.md:0 Link target does not exist: /homework-projects/readme.md
error BROKEN-INTERNAL-LINK legacy/javascript/javascript2/README.md:0 Link target does not exist: /homework-projects/readme.md
error BROKEN-INTERNAL-LINK legacy/javascript/javascript2/week1/README.md:0 Link target does not exist: /homework-projects/readme.md
error BROKEN-INTERNAL-LINK legacy/javascript/javascript2/week1/optional-homework.md:0 Link target does not exist: /homework-projects/readme.md
error BROKEN-INTERNAL-LINK legacy/javascript/javascript2/week1/optional-homework.md:0 Link target does not exist: homework/hyf-bay
error BROKEN-INTERNAL-LINK legacy/javascript/javascript2/week2/README.md:0 Link target does not exist: /homework-projects/readme.md
error BROKEN-INTERNAL-LINK legacy/javascript/javascript2/week2/optional-homework.md:0 Link target does not exist: /homework-projects/readme.md
error BROKEN-INTERNAL-LINK legacy/javascript/javascript2/week2/optional-homework.md:0 Link target does not exist: homework/movies.js
error BROKEN-INTERNAL-LINK legacy/javascript/javascript2/week2/optional-homework.md:0 Link target does not exist: homework/hyf-bay
error BROKEN-INTERNAL-LINK legacy/javascript/javascript2/week3/README.md:0 Link target does not exist: /homework-projects/readme.md
error BROKEN-INTERNAL-LINK legacy/javascript/javascript2/week3/optional-homework.md:0 Link target does not exist: /homework-projects/readme.md
error BROKEN-INTERNAL-LINK legacy/javascript/javascript3/README.md:0 Link target does not exist: /homework-projects/readme.md
error BROKEN-INTERNAL-LINK legacy/javascript/javascript3/README.md:0 Link target does not exist: /homework-projects/readme.md
error BROKEN-INTERNAL-LINK legacy/javascript/javascript3/README.md:0 Link target does not exist: /homework-projects/readme.md
error BROKEN-INTERNAL-LINK legacy/javascript/javascript3/week1/README.md:0 Link target does not exist: /homework-projects/readme.md
error BROKEN-INTERNAL-LINK legacy/javascript/javascript3/week1/optional-homework.md:0 Link target does not exist: /homework-projects/readme.md
error BROKEN-INTERNAL-LINK legacy/javascript/javascript3/week2/README.md:0 Link target does not exist: /homework-projects/readme.md
error BROKEN-INTERNAL-LINK legacy/javascript/javascript3/week2/optional-homework.md:0 Link target does not exist: /homework-projects/readme.md
error BROKEN-INTERNAL-LINK legacy/javascript/javascript3/week3/README.md:0 Link target does not exist: /homework-projects/readme.md
error BROKEN-INTERNAL-LINK legacy/javascript/javascript3/week3/optional-homework.md:0 Link target does not exist: /homework-projects/readme.md
error BROKEN-INTERNAL-LINK legacy/nodejs/week1/README.md:0 Link target does not exist: /week1/preparation.md
error BROKEN-INTERNAL-LINK legacy/nodejs/week1/README.md:0 Link target does not exist: /week1/homework/README.md
error BROKEN-INTERNAL-LINK legacy/nodejs/week1/README.md:0 Link target does not exist: /week1/lesson-plan.md
error BROKEN-INTERNAL-LINK legacy/nodejs/week1/lesson-plan.md:0 Link target does not exist: ../images/atm.jpg
validateLinks: FAIL
markdownlint: ...
markdownlint: PASS
prettier: ...
Checking formatting...
All matched files use Prettier code style!
prettier: PASS
Try './lint --fix' to see if any automatic fixes are possible