docs: add Canada internship job board resource

[hanzili]

Summary

• Adds Hanzilla Jobs as a Canada-specific internship/co-op/new-grad job board in the internship search resources section.
• Keeps the existing recommendation concise and alongside other job-search resources.

Why

University of Manitoba students looking for Canadian internships may benefit from a Canada-specific board that includes internships, co-ops, and early-career roles across Canadian cities.

Test plan

• Markdown-only change; checked git diff --check.