Add linting pre-commit hook, and do linting (#211)

* Add linting pre-commit hook, and do linting

* Bump pre-commit version to v3.4.0, rerun lint on deconflicted changes

Author: oliverli

.gitignore

@@ -26,4 +26,3 @@ pip-selfcheck.json
 
 # Backup files
 *.bak
-

.pre-commit-config.yaml

@@ -0,0 +1,14 @@
+# See https://pre-commit.com for more information
+# See https://pre-commit.com/hooks.html for more hooks
+repos:
+-   repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v3.4.0
+    hooks:
+    -   id: trailing-whitespace
+    -   id: end-of-file-fixer
+    -   id: check-yaml
+    -   id: check-added-large-files
+-   repo: https://github.com/psf/black
+    rev: 20.8b1
+    hooks:
+    -   id: black