Docs: YARD tags for some resources

[pobed2]

This PR introduces YARD tags to document Liquid tags, filters, and objects for public Liquid documentation.

The current content focuses on these elements in the context of Shopify themes.

[shainaraskas]

not accepting category tags on tags not accepting array return types on filters

🔥🔥 Errors detected in YARD tags 🔥🔥
Liquid::If is trying to access unpermitted tag(s): category
Liquid::For is trying to access unpermitted tag(s): category
Liquid::Raw is trying to access unpermitted tag(s): category
Liquid::Case is trying to access unpermitted tag(s): category
Liquid::Echo is trying to access unpermitted tag(s): category
Liquid::Cycle is trying to access unpermitted tag(s): category
Liquid::Render is trying to access unpermitted tag(s): category
Liquid::Unless is trying to access unpermitted tag(s): category
Liquid::Comment is trying to access unpermitted tag(s): category
Liquid::TableRow is trying to access unpermitted tag(s): category
Liquid::If is trying to access unpermitted tag(s): category
Liquid::For is trying to access unpermitted tag(s): category
Liquid::Raw is trying to access unpermitted tag(s): category
Liquid::Case is trying to access unpermitted tag(s): category
Liquid::Echo is trying to access unpermitted tag(s): category
Liquid::Cycle is trying to access unpermitted tag(s): category
Liquid::Render is trying to access unpermitted tag(s): category
Liquid::Unless is trying to access unpermitted tag(s): category
Liquid::Comment is trying to access unpermitted tag(s): category
Liquid::TableRow is trying to access unpermitted tag(s): category
Liquid::StandardFilters#sort:  is an invalid return type, valid return types are: string, number, array, enum, boolean
Liquid::StandardFilters#concat:  is an invalid return type, valid return types are: string, number, array, enum, boolean
Liquid::StandardFilters#sort:  is an invalid return type, valid return types are: string, number, array, enum, boolean
Liquid::StandardFilters#concat:  is an invalid return type, valid return types are: string, number, array, enum, boolean

[pobed2]

@klenotiw @andyw8 FYI I created two tickets to address the issues ^^. https://github.com/Shopify/shopify-dev/issues/17816 and https://github.com/Shopify/shopify-dev/issues/17817

[pobed2]

Oh, lol, I should have looked in the backlog before, there's already something for ^^: https://github.com/Shopify/shopify-dev/issues/17767

[klenotiw]

Shopify/shopify-dev#17767

lol all good I just closed it, I should have probably split it up anyway.