Update Stylelint and its dependencies (#187)

Also drop Node.js < 14 support

Note that we specify lockfile-version=2 for backwards npm compatibility

Author: XhmikosR

.github/workflows/test.yml

@@ -18,7 +18,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        node: [12, 14, 16, 18]
+        node: [14, 16, 18]
 
     steps:
       - name: Clone repository

.npmrc

@@ -0,0 +1 @@
+lockfile-version=2