refactor RDoc markup handling for improved loading and initialization

[seuros]

Description

rdoc class had support for a rdoc version that is 12 years old.

added https for the homepage.

Completed Tasks

• I have read the Contributing Guide.
• The pull request is complete (implemented / written).
• Git commits have been cleaned up (squash WIP / revert commits).
• I wrote tests and ran bundle exec rake locally (if code is attached to PR).

[lsegal]

This seems to fail all tests. Can you look into this?

[seuros]

Oh cool, i see you dropped legacy support for 2.6.

Do you think we should go at a safer zone to support only 3.2+ since anything before is EOL.

I have some yard plugins that work only in those version as they use edge gem or ruby features.

[lsegal]

(oops earlier comment was incorrect)

We would need to support ruby 2.x+ even if we can't run CI tests against them. CI doesn't represent what versions of ruby yard supports.

[seuros]

Remember that dropping support doesn't mean that version 2.x cannot install yard suddenly.

It just means that future versions won't be installable.

Those legacy versions don't even install in recent hardware like Apple Silicon, and lot it dependencies are EOL or have huge security problem (eg: openssl 3 compatibility).