Adding GitHub repos to doc server

chrome/common/extensions/docs/templates/json/content_providers.json

 // === Overview ===
 //
 // This file configures where to find and how to serve content in the docserver.
 // It's the most fundamentally important file in all of the docserver.
 //
 // === Format ===
 //
 // Each entry declares a rule with:
 //  * An arbitrary identifier key e.g. "cr-extensions-examples".
 //  * What URL the rule should be invoked with, given by "serveFrom", e.g.
@@ skipping 42 matching lines @@
       "dir": "docs/templates/public"
     },
     "serveFrom": "",
     "supportsTemplates": true
   },
   "cr-static": {
     "chromium": {
       "dir": "docs/static"
     },
     "serveFrom": "static"
+  },
+  "devtools-docs": {
+    "github": {
+      "owner": "GoogleChrome",
+      "repo": "devtools-docs-migration"
+    },
+    "serveFrom": "devtools"
+  },
+  "multidevice-docs": {
+    "github": {
+      "owner": "GoogleChrome",
+      "repo": "multi-device"
+    },
+    "serveFrom": "multidevice"
+  },
+  "webstore-docs": {
+    "github": {
+      "owner": "GoogleChrome",
+      "repo": "webstore-docs"
+    },
+    "serveFrom": "webstore"
   }
 }