Add CONTRIBUTING with some basic info

Author: michaelpj

CONTRIBUTING.md

@@ -0,0 +1,22 @@
+# Contributing
+ 
+## Versioning policy
+
+`lsp` and `lsp-types` should typically have identical versions and be released in lockstep.
+This is for two reasons:
+1. They are morally one package, and may become one again once multiple public libraries are better supported.
+2. `lsp` exports many types from `lsp-types`, so in practice will need a major verison bump when `lsp-types` does anyway.
+
+`lsp-test` can evolve independently.
+
+## Git tags
+
+The tagging scheme is `$package-$version`, e.g. `lsp-types-1.0.0`.
+
+## Making a release
+
+1. Bump version numbers as needed (see 'Versioning policy')
+2. Update changelogs (currently manual, sadly)
+3. Once the above is in master, create git tags following 'Git tags'
+4. Create package candidates for the packages, and check that they all look good.
+5. Finalize the package candidates.