Update readme.md.

* fix typos
* use a code block for the local commands
Update .gitignore and _config.yml.

Ignore "package.json" in _config.yml too.
Use the https links to the github projects for consistency.
Remove stray space after `alt=`.
index.html: remove unneeded class.

It's inherited from `ul`.
Use a 16x16 favicon.ico.