Auto generate README.md for all versions listings

There should be README.md files inside of a distribution version listing, and inside each version listing.

Eg from https://github.com/ipfs/distributions#how-this-repo-works:

```
dist/index.html -- listing of all bundles available
dist/ -- all versions of
dist//README.md -- simple readme for
dist//latest -- points to latest
dist// -- dist version
dist///README.md -- readme for listing
```

these READMEs can be the same across versions, and should be autogenerated. They are like a human readable version of `dist.json`, there in case the user ends up with a big archive directory of the version. The readme could point to https://dist.ipfs.io, could point to this repository, and to `https://ipfs.io