docs: add homepage link to @babel/runtime package.json (#10418)

* docs: add homepage link

Adds a homepage link to populate npmjs.com.
Update the repository property syntax.

* Update the repository link

Point to the root repo plus a reference to the subdirectory.

* style: drop HTML extension

packages/babel-runtime/package.json

@@ -6,7 +6,12 @@
   "publishConfig": {
     "access": "public"
   },
-  "repository": "https://github.com/babel/babel/tree/master/packages/babel-runtime",
+  "repository": {
+    "type" : "git",
+    "url" : "https://github.com/babel/babel.git",
+    "directory": "packages/babel-runtime"
+  },
+  "homepage": "https://babeljs.io/docs/en/next/babel-runtime",
   "author": "Sebastian McKenzie <sebmck@gmail.com>",
   "dependencies": {
     "regenerator-runtime": "^0.13.2"