Add flynt as pre-commit hook

Author: Skylion007

.pre-commit-config.yaml

@@ -37,6 +37,12 @@ repos:
   - id: pyupgrade
     args: [--py36-plus]
 
+# Always convert to fstrings
+- repo: https://github.com/ikamensh/flynt/
+  rev: "0.76"
+  hooks:
+  - id: flynt
+
 # Nicely sort includes
 - repo: https://github.com/PyCQA/isort
   rev: 5.10.1