fix(api.md): fix some nits in API.md (#71)
fix(api.md): fix some nits in API.md (#71)

* Fix typos.
* Fix link anchors.
* Fix sorting of sections and references.
* Fix copy-paste artifacts.
* Fix formatting/markdown issues.

* Unify casing and punctuation.
* Unify using template literals instead of string concatenation.

* Add missing types.
* Add missing return values.
* Add method descriptions.
* Add backticks for API entities.
* Add quotes to emphasize string value types.
GoogleChromeLabs/carlo,GoogleChromeLabs/carlo