docs: add rolling.md (microsoft#859)

Co-authored-by: Max Schmitt <[email protected]>

Author: aslushnikov

ROLLING.md

@@ -0,0 +1,16 @@
+# Rolling Playwright-Python to the latest Playwright driver
+
+* checkout repo: `git clone https://github.com/microsoft/playwright-python`
+* make sure local python is 3.9
+    * create virtual environment, if don't have one: `python -m venv env`
+* activate venv: `source env/bin/activate`
+* install all deps:
+     - `python -m pip install --upgrade pip`
+     - `pip install -r local-requirements.txt`
+     - `pre-commit install`
+     - `pip install -e .`
+* change driver version in `setup.py`
+* download new driver: `python setup.py bdist_wheel`
+* generate API: `./scripts/update_api.sh`
+* commit changes & send PR
+* wait for bots to pass & merge the PR