docs: Add contributing rules

contributing.md

@@ -0,0 +1,44 @@
+# Contributing to FingerprintJS Pro Google Tag Manager
+
+## Working with code
+
+We prefer using [yarn](https://yarnpkg.com/) for installing dependencies and running scripts.
+
+The master branch is locked for the push action. For proposing changes, use the standard [pull request approach](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/creating-a-pull-request). It's recommended to discuss fixes or new functionality in the Issues, first.
+
+### How to build
+Just run:
+```shell
+yarn build
+```
+
+### Code style
+
+The code style is controlled by [ESLint](https://eslint.org/) and [Prettier](https://prettier.io/). Run to check that the code style is ok:
+```shell
+yarn lint
+```
+
+You aren't required to run the check manually, the CI will do it. Run the following command to fix style issues (not all issues can be fixed automatically):
+```shell
+yarn lint:fix
+```
+
+### How to test
+Tests are located in `__tests__` folder and run by [jest](https://jestjs.io/) in [jsdom](https://github.com/jsdom/jsdom) environment.
+
+To run tests you can use IDE instruments or just run:
+```shell
+yarn test
+```
+
+To check the Typescript types, run:
+```shell
+yarn typecheck
+```
+
+### How to publish
+- Create a new branch
+- Run `yarn release:(major|minor|patch)` depending on the version you need
+- Make a pull request
+- After merging the pull request into the main branch and after successful tests, GitHub Action will publish a new version to the npm