Turn more of the index.html body contents into templates

[UPLYNXED]

Primarily so that any changes to the layout of the page doesn't require replacing index.html in active installations due to the title and meta tag customization being required to be done in it due to social media link embedding limitations.

Related to #5, keep template file size in mind.

Potentially move page layout templates to a separate file from the tweets layout templates?

• Make a new issue out of this when it comes to this point.