📝 Comprehensive coverage.py configuration documentation

This is a follow up for #10 with dedicated configuration section.

README.md

@@ -10,13 +10,8 @@ GitHub Action for Python [Coveralls.io](https://coveralls.io/)
 
 
 ## Usage
-First make sure your `coverage.py` is configured with [`relative_files = True`](https://coverage.readthedocs.io/en/coverage-5.0.4/config.html#config-run-relative-files), i.e. create or edit your `.coveragerc` file in your repository to include the setting
-
-```
-[run]
-relative_files = True
-```
-
+First make sure your `coverage.py` is configured with [`relative_files = True`](https://coverage.readthedocs.io/en/coverage-5.2.1/config.html#config-run-relative-files).
+See the [Coverage.py configuration](#coveragepy-configuration) section for examples.
 If this setting is missing you will likely get an error "not a git repository".
 
 Then assuming you have a `make test` that runs coverage testing.
@@ -75,3 +70,30 @@ jobs:
     # Default: false
     debug: ''
 ```
+
+## Coverage.py configuration
+
+The `relative_files = True` setting can be handled via different files such as `.coveragerc`, `tox.ini` and more, all covered in the examples below.
+Also see the [Coverage.py configuration reference](https://coverage.readthedocs.io/en/coverage-5.2.1/config.html#configuration-reference) for full details.
+
+### .coveragerc
+Under the `[run]` section:
+```ini
+[run]
+relative_files = True
+```
+
+### setup.cfg or tox.ini
+Under the `[coverage:run]` section:
+```ini
+[coverage:run]
+relative_files = True
+```
+
+### pyproject.toml
+Under the `[tool.coverage.run]` section.
+It also requires `coverage` to be installed with the `toml` extra (`pip install coverage[toml]`):
+```ini
+[tool.coverage.run]
+relative_files = True
+```