Fix Shortcode context for v2 blocks

[Agos95]

Purpose

Shortcodes in the new block system do not get access to the correct .Page variable (see #2918 ). The problem is the use of markdownify function to parse $block.content.text, since it actually is an alias to site.Home.RenderString since v 0.93.0 (see gohugoio/hugo#9959 (comment)).

This causes the shortcodes to always get the Homepage as .Page variable. The fix is to substitute markdownify with $page.RenderString, which gives the correct context.

An actual example of this behaviour can be found in this branch (in the csv page):

This PR fixes #2918.

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[gcushen]

Thanks for contributing a solution 🎉

Before we merge this, can you check if we still need to include the emojify logic or if Hugo is now smart enough to use the emojify: true site setting in config.yaml in its RenderString function?

[Agos95]

I tried, but emojify logic is still required to render emoji.