Update JS dependencies (#15033)

* Update JS dependencies

- Update all JS dependencies
- For octicons, rename trashcan to trash
- For svgo, migrate to v2 api, output seems to have slightly changed but icons look the same
- For stylelint, update config, fix custom property duplicates
- For monaco, drop legacy Edge support
- For eslint, enable new rules, fix new issues
- For less-loader, remove deprecated import syntax

* update svgo usage in generate-images and rebuild logo.svg with it

public/img/svg/octicon-chevron-left.svg

@@ -1 +1 @@
-<svg viewBox="0 0 16 16" class="svg octicon-chevron-left" width="16" height="16" aria-hidden="true"><path fill-rule="evenodd" d="M9.78 12.78a.75.75 0 01-1.06 0L4.47 8.53a.75.75 0 010-1.06l4.25-4.25a.75.75 0 011.06 1.06L6.06 8l3.72 3.72a.75.75 0 010 1.06z"/></svg>
+<svg viewBox="0 0 16 16" class="svg octicon-chevron-left" width="16" height="16" aria-hidden="true"><path fill-rule="evenodd" d="M9.78 12.78a.75.75 0 0 1-1.06 0L4.47 8.53a.75.75 0 0 1 0-1.06l4.25-4.25a.75.75 0 0 1 1.06 1.06L6.06 8l3.72 3.72a.75.75 0 0 1 0 1.06z"/></svg>