Add documentation for all functions and add necessary tooling to catch these errors.

[krishnasrinivas]

@harshavardhana

• as a priority, the commit has comments for only exposed APIs, I will add comments to the rest of the functions as a lower priority. we can keep the bug open.
• Also I will change the commenting style so that we can use tools like https://github.com/jsdoc2md/jsdoc-to-markdown or https://github.com/cbou/markdox