use preact for common components across site (#663)

* convert GitHub cards grid from lit-html to preact

* give hit counter the preact treatment

* extract loading spinner component to a shared location

* move *some* loading spinner styles to its JSX

* Update .percy.yml

* pick up images in JS w/ webpack

* pull star/fork icons straight from @primer/octicons

* a bit of cleanup

* check `typeof window !== "undefined"` before rendering

* bump misc. deps

* silence missing license warnings for preact-hooks and preact-compat

* add source-map-loader

* Update loading.js

.eslintrc.cjs

@@ -2,9 +2,9 @@ module.exports = {
   root: true,
   extends: [
     "@jakejarvis/eslint-config",
+    "preact",
     "plugin:compat/recommended",
     "plugin:import/recommended",
-    "plugin:lit/recommended",
     "plugin:no-unsanitized/DOM",
     "plugin:prettier/recommended",
   ],