[DOCS] CONTRIBUTING

Refs: https://codeberg.org/forgejo/forgejo/issues/8
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/153
Refs: https://codeberg.org/forgejo/forgejo/issues/123
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/299
(cherry picked from commit 08dcef0c8c)

[DOCS] CONTRIBUTING/RELEASE: https://forgejo.org/docs/admin

Because the version is not displayed on the landing page of Forgejo,
there cannot be a link to a versionned documentation. There must exist
a link that points to the latest version on the website for the
forgejo instance to display.

Better but more complicated approaches could be to:

* Embed the documentation in Forgejo
* Allow the admin to not display the help
* Allow the admin to display a versionned help or not

(cherry picked from commit 83cc389239)
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(cherry picked from commit 9a66b3d70b)

[DOCS] CONTRIBUTING/RELEASE: reminder to update FORGEJO_VERSION

(cherry picked from commit 2a4d0bd164)
(cherry picked from commit d68576ba67)

[DOCS] CONTRIBUTING: updates

* Remove obsolete description of the well being & moderation team and
  replace them with a link to the moderation email.

* Remove description of the governance process and replace with a link
  to the governance readme that did not exist at the time.

* Add links to the Forgejo documentation

(cherry picked from commit df749da272)
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[DOCS] CONTRIBUTING (squash)

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[DOCS] Add link to build instructions in CONTRIBUTING.md

(cherry picked from commit 50d86aa4ad)

Replace 'v1.20' with 'next'

(cherry picked from commit 3e99f49fc5)

CONTRIBUTING.md

@@ -0,0 +1,24 @@
+# Forgejo Contributor Guide
+
+The Forgejo project is run by a community of people who are expected to follow this guide when cooperating on a simple bug fix as well as when changing the governance. For more information about the project, take a look at [the documentation explaining what Forgejo provides](README.md).
+
+Sensitive security-related issues should be reported to [security@forgejo.org](mailto:security@forgejo.org) using [encryption](https://keyoxide.org/security@forgejo.org).
+
+## For everyone involved
+
+- [Documentation](https://forgejo.org/docs/next/)
+- [Code of Conduct](https://forgejo.org/docs/next/developer/COC/)
+- [Bugs, features, security and others discussions](https://forgejo.org/docs/next/developer/DISCUSSIONS/)
+- [Governance](https://forgejo.org/docs/next/developer/GOVERNANCE/)
+- [Sustainability and funding](https://codeberg.org/forgejo/sustainability/src/branch/master/README.md)
+
+## For contributors
+
+- [Developer Certificate of Origin (DCO)](https://forgejo.org/docs/next/developer/DCO/)
+- [Development workflow](https://forgejo.org/docs/next/developer/WORKFLOW/)
+- [Compiling from source](https://forgejo.org/docs/next/developer/from-source/)
+
+## For maintainers
+
+- [Release management](https://forgejo.org/docs/next/developer/RELEASE/)
+- [Secrets](https://forgejo.org/docs/next/developer/SECRETS/)