Sort some badges (#1945)

This implements proposals 1, 2, and 4 from #1905:

* Move gem rank from ratings to downloads; tweak title

* Move docker build from other to build

* Move bundlephobia, github file, github repo, imagelayers, and microbadger size + layers badges into new category

* Fill in a couple missing titles

services/gem/gem-rank.service.js

@@ -61,7 +61,7 @@ module.exports = class GemRank extends BaseJsonService {
   }
 
   static get category() {
-    return 'rating'
+    return 'downloads'
   }
 
   static get url() {
@@ -75,12 +75,12 @@ module.exports = class GemRank extends BaseJsonService {
   static get examples() {
     return [
       {
-        title: 'Gems',
+        title: 'Gem download rank',
         previewUrl: 'rt/puppet',
         keywords: ['ruby'],
       },
       {
-        title: 'Gems',
+        title: 'Gem download rank (daily)',
         previewUrl: 'rd/facter',
         keywords: ['ruby'],
       },