Setting up prettier

In order not to wreak havoc on all the open PRs, Prettier will be added slowly,
on every changed file, thanks to Husky (for a precommit hook) and lint-staged, for linting only staged files.

.husky/.gitignore

@@ -0,0 +1 @@
+_

.husky/pre-commit

@@ -0,0 +1,4 @@
+#!/bin/sh
+. "$(dirname "$0")/_/husky.sh"
+
+cd front && yarn run precommit