Readme: New Building and Contributing section. Fix #101

Thanks moparisthebest for typos

Signed-off-by: Maxime “pep” Buquet <pep@bouah.net>

README.md

@@ -25,3 +25,52 @@ License
 -------
 
 Mozilla Public License 2 (MPL2). See the LICENSE file.
+
+Building
+--------
+
+Dependencies should be provided by crates if you use the default features. If
+you use tokio-xmpp's `tls-native` feature you will need an ssl library
+(openssl, libressl, etc.).
+
+```
+cargo build
+```
+
+The various features available should be explained in the crates themselves.
+
+Contributing
+------------
+
+Thank you for your interest in the project!
+
+We recommend you come and talk to us in the channel and/or open an issue
+before you start working on a feature, to see if it aligns with our goals.
+
+The library is still in development, and while this is the case we adopt a
+fail-fast strategy, which is also a reason for the choice of the language.
+
+The earlier we catch bugs and fix them, the less chances they have to confuse
+users of our library, or make end-users give up on software developed using
+this library. This also helps improving other software in the ecosystem.
+
+Code changes should try to include documentation as possible. They should also
+include tests where appropriate, and pass the existing test suite.
+
+CI should pass to submit your changes. This is done by ensuring `cargo fmt`
+and `cargo test` pass (in the workspace).
+
+More thorough tests can be done locally with `act exec` or `forgejo-runner
+exec`, which is also what is run in the CI. We require docker to be setup for
+this to work.
+
+Merge requests can contain as many commits as necessary, but commits should be
+kept rather small and meaningful (not include too many different things).
+
+Do not forget to update changelogs and other crate metadata where necessary.
+
+Signing commits (`git commit -S`) and adding DCO bits (`git commit -s`) are
+welcome but not mandatory.
+
+We'll do our best to review and discuss changes with you but we're also humans
+with other activities, please be patient with us.