docs: rewrite README; deployment, usage and contributing guides; credits

.all-contributorsrc

@@ -0,0 +1,14 @@
+{
+  "projectName": "reframe",
+  "projectOwner": "reframe-oss",
+  "repoType": "github",
+  "repoHost": "https://github.com",
+  "files": [".github/ALL_CONTRIBUTORS.md"],
+  "imageSize": 80,
+  "commit": false,
+  "commitConvention": "angular",
+  "contributorsPerLine": 7,
+  "linkToUsage": false,
+  "skipCi": true,
+  "contributors": []
+}

.github/ALL_CONTRIBUTORS.md

@@ -0,0 +1,48 @@
+# Everyone who helps Reframe
+
+Code contributors appear automatically in the
+[README](../README.md#contributors) through contrib.rocks. This page also
+credits work that doesn't show up as commits: reviews, mentoring, design,
+testing, translations, docs feedback, ideas and community support. It follows
+the [all-contributors](https://allcontributors.org) specification.
+
+<!-- ALL-CONTRIBUTORS-LIST:START - Do not remove or modify this section -->
+<!-- prettier-ignore-start -->
+<!-- markdownlint-disable -->
+
+<!-- markdownlint-restore -->
+<!-- prettier-ignore-end -->
+<!-- ALL-CONTRIBUTORS-LIST:END -->
+
+## Adding someone (maintainers)
+
+Nobody is added automatically. A maintainer adds each person, with their
+agreement, using one of these:
+
+**With the all-contributors bot** (install the
+[GitHub App](https://allcontributors.org/docs/en/bot/installation) on
+reframe-oss/reframe once). Then comment on any issue or pull request:
+
+```
+@all-contributors please add @username for review, mentoring
+```
+
+The bot opens a pull request that updates `.all-contributorsrc` and the list
+above. Review and merge it like any other PR.
+
+**With the CLI**, from a branch:
+
+```bash
+bunx all-contributors-cli add username review,mentoring
+bunx all-contributors-cli generate
+```
+
+Commit `.all-contributorsrc` and this file, and open a pull request.
+
+Common contribution types: `review`, `mentoring`, `design`, `ideas`, `bug`,
+`userTesting`, `doc`, `translation`, `question` (answering questions),
+`eventOrganizing`, `maintenance`, `security`, `a11y`. The full list is in the
+[emoji key](https://allcontributors.org/docs/en/emoji-key).
+
+GSSoC points are separate: they come from the `gssoc:approved` label on merged
+pull requests, not from this list.

CODE_OF_CONDUCT.md

@@ -36,7 +36,7 @@ This Code of Conduct applies within all community spaces, and also applies when
 
 ## Enforcement
 
-Instances of abusive, harassing, or otherwise unacceptable behavior may be reported to the community leaders responsible for enforcement at [INSERT CONTACT METHOD]. All complaints will be reviewed and investigated promptly and fairly.
+Instances of abusive, harassing, or otherwise unacceptable behavior may be reported to the community leaders responsible for enforcement at <!-- TODO(maintainer): add a private conduct contact (a project email address). --> **TODO: a private contact address will be added here.** Until then, use GitHub's [report abuse](https://docs.github.com/en/communities/maintaining-your-safety-on-github/reporting-abuse-or-spam) form, or tag a maintainer ([@magic-peach](https://github.com/magic-peach)) on an issue asking them to get in touch. All complaints will be reviewed and investigated promptly and fairly.
 
 All community leaders are obligated to respect the privacy and security of the reporter of any incident.