Summary:
Explain the **motivation** for making this change. What existing problem does the pull request solve?
I had tried fixing a broken link in a previous commit (#11453). My commit was merged, but it did not resolve the underlying problem. I have looked into how links should be formed for the docs and have fixed the original problem as well as updated all other links to be consistent.
Previous link formats:
- /docs/sample.html <-- broken link
- sample.html <-- broken link
- https://facebook.github.io/react-native/docs/sample.html <-- works
- /react-native/docs/sample.html <-- works
- docs/sample.html <-- works (permalink format)
This PR updates all links to the permalink format.
**Test plan (required)**
I ran the website locally and manually tested half of the links in each category. They all worked.
```
$ cd website
$ npm install && npm start
```
Closes https://github.com/facebook/react-native/pull/12064
Differential Revision: D4489153
Pulled By: mkonicek
fbshipit-source-id: bf0231d941ba147317595c3b3466dc579a887169
8378f0f9f7