flake8: add page (#6275)

pages/common/flake8.md

@@ -0,0 +1,20 @@
+# flake8
+
+> Tool to check the style and quality of Python code.
+> More information: <https://flake8.pycqa.org/>.
+
+- Lint a file or directory recursively:
+
+`flake8 {{path/to/file_or_directory}}`
+
+- Lint a file or directory recursively and show the line on which each error occurred:
+
+`flake8 --show-source {{path/to/file_or_directory}}`
+
+- Lint a file or directory recursively and ignore a list of rules. (All available rules can be found at flake8rules.com):
+
+`flake8 --ignore {{rule1,rule2}} {{path/to/file_or_directory}}`
+
+- Lint a file or directory recursively but exclude files matching the given globs or substrings:
+
+`flake8 --exclude {{substring1,glob2}} {{path/to/file_or_directory}}`