Merge branch 'css-selector-format' into 'master'

Disabled SelectorFormat rule for SCSS Lint in order to get the Rake
task passing sooner.

SelectorFormat enforces that CSS classes and IDs use lowercase
hyphenated style, `like-this`, but a not-insignificant amount of
selectors in the codebase are `like_this`.

Fixing the selectors that break this rule would require changing HTML
as well, and potentially break JavaScript hooks, among other things. So
I decided to disable this rule for the time being, hopefully making it
easier to fix all the remaining warnings SCSS Lint is giving by removing
the most problematic rule.

Discussed in #14299.

See merge request !3309

.scss-lint.yml

@@ -100,7 +100,7 @@ linters:
   # Selectors should always use hyphenated-lowercase, rather than camelCase or
   # snake_case.
   SelectorFormat:
-    enabled: true
+    enabled: false
     convention: hyphenated_lowercase
   
   # Prefer the shortest shorthand form possible for properties that support it.