Migrate to documentationjs version with typescript support

[bodia-uz]

Currently to support typescript, we use a hack - parse typescript and cleanup a code that is not parsable by documentationjs flow based parser.
documentationjs finally supports typescript, so now we could migrate to new version and get rid of logic like:
https://github.com/wix/okidoc/blob/1affa46a1b25359d45a553f06bd58cb9e58cdcd5/packages/okidoc-md/src/utils/nodeAST.js#L54-L59