CI: add docs_full label info to readme
- `custom_test[_esp32/esp32s2/...]`
- `docker`
- `docs`
+- `docs_full`, triggers a full docs build, not a fast build which is the CI default. This includes PDF and doxygen generated API documentation.
- `example_test[_esp32/esp32s2/...]`
- `fuzzer_test`
- `host_test`
