Tidy up contributing docs (#952)

Author: charisk

CONTRIBUTING.md

@@ -3,5 +3,16 @@
 - Install the recommended extensions for automatic formatting on save.
 - We use the [ava](https://github.com/avajs/ava) test runner. To run one or more specific test(s), use `npm run test -- -m <title>`.
 - The `codeql` executable must be on the path before running any tests.
-- All compiled artifacts and `node_modules` dependencies should be checked in.
+- All compiled artifacts should be checked in.
 - We recommend running `npm run watch` in the background to keep compiled artifacts up to date during development.
+
+# Generating sourcemaps
+
+In case you want to generate sourcemaps for tracing back a specific line in a stacktrace to the source code, you can
+use the following command:
+
+```shell
+CODEQL_VARIANT_ANALYSIS_ACTION_GENERATE_SOURCEMAPS=true npm run build
+```
+
+The sourcemaps will be placed in the `dist` directory.

README.md

@@ -3,14 +3,3 @@
 This action is used internally by GitHub's multi-repository variant analysis. It is not intended to be used directly.
 
 If you want to use CodeQL to analyze your source code, please see the [CodeQL Action](https://github.com/github/codeql-action) and the [Code scanning documentation](https://docs.github.com/en/code-security/code-scanning/automatically-scanning-your-code-for-vulnerabilities-and-errors/about-code-scanning).
-
-### Generating sourcemaps
-
-In case you want to generate sourcemaps for tracing back a specific line in a stacktrace to the source code, you can
-use the following command:
-
-```shell
-CODEQL_VARIANT_ANALYSIS_ACTION_GENERATE_SOURCEMAPS=true npm run build
-```
-
-The sourcemaps will be placed in the `dist` directory.