[SEO/AEO] Add best practices to codebase and documentation

[joshuapease]

AEO

llms.txt

We're somewhat skeptical about the practical value of llms.txt. But there's no harm giving clients the option of customizing this URL route.

The easiest solution would be to add a Global field for llms.txt and a custom route that renders https://mydomain.test/llms.txt

There are also some Craft plugins for this too... I'm personally hesitant to bring in third-party code for something this simple.

SEO

Pagination

@maxfenton found this snippet handy for establishing canonical best practices on paginated features.

• https://nystudio107.com/docs/seomatic/using/pagination.html

{% if seomatic is defined %}
  {% do seomatic.helper.paginate(pageInfo) %}
{% endif %}