Add Contributing guide

CONTRIBUTING.md

@@ -0,0 +1,35 @@
+# Contributing Guide
+
+## Updating dependencies
+
+1. You can update the Toolkit dependencies in `Toolkit.scala`, `Toolkit.js.scala` and `ToolkitTest.scala`. The versions in `Toolkit.scala` and `Toolkit.js.scala` should be the same.
+
+2. After changing the dependencies, you must generate the changelog:
+
+- Check that the config in `changelog/Config.scala` is up-to-date: `releaseVersion` should contain the latest released version and `developmentVersion` should contain the next version to release.
+- Run `scala-cli run changelog -- --overwrite` to generate the changelog
+- If the generation fails because of illegal version bumps, you can add the development version in `exceptions.txt` and run `scala-cli run changelog -- --overwrite` again. (This won't be permitted anymore after 1.0.0 which will be the first stable version)
+- Commit and push the changes in the changelog
+
+## Releasing the Toolkit
+
+1. [Create a new release](https://github.com/scala/toolkit/releases/new) in the Github repo
+
+2. Create a new `0.x.y` tag in the `Choose a tag` dropdown list
+
+3. Copy, paste the release description below, and update the versions:
+
+```md
+## Changes to direct dependencies for toolkit
+ - Updated `com.lihaoyi:os-lib` from `0.10.0` to `0.10.3`
+ - Updated `com.lihaoyi:upickle` from `3.3.0` to `3.3.1`
+ - Updated `com.softwaremill.sttp.client4:core` from `4.0.0-M14` to `4.0.0-M16`
+ - Updated `com.softwaremill.sttp.client4:upickle` from `4.0.0-M14` to `4.0.0-M16`
+
+## Changes to direct dependencies for toolkit-test
+ - Updated `org.scalameta:munit` from `1.0.0-M11` to `1.0.0`
+```
+
+4. Validate by clicking the `Publish release` button.
+
+5. Check that the `Publish toolkit` action starts, and runs successfully. The new version should appear on [Maven Central](https://repo1.maven.org/maven2/org/scala-lang/toolkit-test_3/) after some time.

README.md

@@ -14,8 +14,6 @@ Or by including the latest Toolkit artifact in your build file: `org.scala-lang:
 ## Dependencies changelog
 In the `changelog` directory you can find a list of changes in the dependencies of the Scala Toolkit, including transitive ones.
 
-### Generate or update changelog
-To generate or update the changelog, run the following command:
-```shell
-scala-cli changelog -- --overwrite
-```
+## How to update the dependencies? How to release the toolkit?
+
+Check out the [Contributing Guide](CONTRIBUTING.md).