Add annotations to typealiases and typealiases to EJS template contexts

[fabianmuecke]

Right now type aliases do have an annotations property, but it's empty, although the annotations of aliases do get parsed. I'd like to fix that, so type aliases can also be annotated as entry points for templates.

I'll need the type aliases to be available in EJS template contexts as well.

I've opened a PR with both changes here. Please let me know, what you think.