[ci] Exclude node_modules from Black and RST checks

- Added pyproject.toml with Black config to exclude node_modules
- Modified run-qa-checks to skip RST check in openwisp-qa-check
  and run it separately with node_modules excluded

Author: nemesifier

pyproject.toml

@@ -0,0 +1,4 @@
+[tool.black]
+extend-exclude = '''
+/(node_modules|\.venv|venv)/
+'''

run-qa-checks

@@ -14,3 +14,7 @@ openwisp-qa-check \
     --skip-checkmigrations \
     --skip-checkmakemigrations \
     --skip-checkendline \
+    --skip-checkrst
+
+# Run RST check separately with node_modules excluded
+docstrfmt --no-docstring-trailing-line -c -l 74 -s "=-~+^\"'.:" --extend-exclude node_modules .