Build and publish docs in CI

Since we do not want to store api docs in the repo (too big, change too often), we should create a nice place to host them.

For the beginning, we can request devs to generate locally, but this is a pain point and barrier to entry, which we want to make as easy as possible for anyone looking to build in the iov ecosytem.

yarn docs in the main package will build them all, we need to think of a hosting strategy, and then link them from the READMEs, so all npm packages have a link to current docs (on master? last tag??)

[rudi-cilibrasi]

yes the only problem with pushing to gh-pages or github pages is that the repo with source code gets so big and loses density. this can be remedied by simply pushing docs to a docs-only repo that is named the same as the subject of the docs but has a prefix or suffix added to the repo-name like -doc. i push docs to gh-pages here and it has worked great for years http://rudi-cilibrasi.github.io/zlibcomplete/ for free too

[webmaster128]

looks like some of the links are broken https://iov-one.github.io/iov-core-docs/latest/iov-tendermint-rpc/index.html

Thanks, fixed. This was a github pages configuration, ignoring files tat start with _.