Add Applicable checklists and extensions section into MIxS docs

[sujaypatil96]

In this PR we are seeking to add the Applicable Checklists and Extensions section to the term documentation pages (to be able to link from the term back to the checklists and extensions on the main landing page that use them)

For example, the term documentation page for HACCP_term will look like this:

[sujaypatil96]

Update have been made based on the dicussion/feedback captured at TWG meeting on 3/5. See notes doc here.

I propose merging this soon since this update has been pending for a while. The longer it is open, the harder it gets to resolve merge conflicts in forks, etc.

[sujaypatil96]

See this feature applied to my fork of the mixs docs live: https://sujaypatil96.github.io/mixs/0001215/

[only1chunts]

That looks great on the link you gave! thanks.