add docs:fork

This makes it easier to auto-generate docs when a contributor has forked the repo. See #439 (comment) for more information

Author: jhuleatt

.github/CONTRIBUTING.md

@@ -85,3 +85,4 @@ set up.
 3. run `yarn lint` to confirm that code meets our style guide
     > If the lint check fails, run `yarn lint --fix` to automatically fix any issues. 
 5. run `yarn docs` to rebuild the reference docs
+    > If you've forked the repo, run `yarn docs:fork` instead. This will ensure the reference docs link to the firebaseextended/reactfire repository.

package.json

@@ -23,7 +23,8 @@
     "lint": "tsdx lint src test",
     "size": "size-limit",
     "analyze": "size-limit --why",
-    "docs": "typedoc --options typedoc.json && markdown-toc -i docs/use.md"
+    "docs": "typedoc --options typedoc.json && markdown-toc -i docs/use.md",
+    "docs:fork": "typedoc --options typedoc.json --gitRemote upstream && markdown-toc -i docs/use.md"
   },
   "peerDependencies": {
     "firebase": "^9.0.0",