Auto merge of rust-lang#17095 - Veykril:contributing.md, r=Veykril

Add CONTRIBUTING.md

I'm not great with these kinds of documents, but the main point I want to be able to raise is that feature implementations should have an issue raised first for discussion.

src/tools/rust-analyzer/CONTRIBUTING.md

@@ -0,0 +1,30 @@
+# Contributing to rust-analyzer
+
+Thank you for your interest in contributing to rust-analyzer! There are many ways to contribute
+and we appreciate all of them.
+
+To get a quick overview of the crates and structure of the project take a look at the
+[./docs/dev](./docs/dev) folder.
+
+If you have any questions please ask them in the [rust-analyzer zulip stream](
+https://rust-lang.zulipchat.com/#narrow/stream/185405-t-compiler.2Frust-analyzer) or if unsure where
+to start out when working on a concrete issue drop a comment on the related issue for mentoring
+instructions (general discussions are recommended to happen on zulip though).
+
+## Fixing a bug or improving a feature
+
+Generally it's fine to just work on these kinds of things and put a pull-request out for it. If there
+is an issue accompanying it make sure to link it in the pull request description so it can be closed
+afterwards or linked for context.
+
+If you want to find something to fix or work on keep a look out for the `C-bug` and `C-enhancement`
+labels.
+
+## Implementing a new feature
+
+It's advised to first open an issue for any kind of new feature so the team can tell upfront whether
+the feature is desirable or not before any implementation work happens. We want to minimize the
+possibility of someone putting a lot of work into a feature that is then going to waste as we deem
+it out of scope (be it due to generally not fitting in with rust-analyzer, or just not having the
+maintenance capacity). If there already is a feature issue open but it is not clear whether it is
+considered accepted feel free to just drop a comment and ask!

src/tools/rust-analyzer/README.md

@@ -13,8 +13,9 @@ https://rust-analyzer.github.io/manual.html#installation
 
 ## Documentation
 
-If you want to **contribute** to rust-analyzer or are just curious about how
-things work under the hood, check the [./docs/dev](./docs/dev) folder.
+If you want to **contribute** to rust-analyzer check out the [CONTRIBUTING.md](./CONTRIBUTING.md) or
+if you are just curious about how things work under the hood, check the [./docs/dev](./docs/dev)
+folder.
 
 If you want to **use** rust-analyzer's language server with your editor of
 choice, check [the manual](https://rust-analyzer.github.io/manual.html) folder.