* website: bump to docs-page prerelease with hidden page support

* website: remove temp check for hidden pages, covered by docs-page

* website: bump to stable docs-page, w next-mdx-remote bump

* website: add unlinked content check

* website: remove unused guides-navigation.js

* adds issue templates for bugs and features, links to discuss and learn guides

* fix smart quotes

This fixes the version reference error seen in this workflow failure:
https://github.com/hashicorp/nomad/actions/runs/504695096

I’ve also included an update to the sticky comment action version to address this warning in the above link:

marocchino/sticky-pull-request-comment@33a6cfb looks like the shortened version of a commit SHA. Referencing actions by the short SHA will be disabled soon. Please see https://docs.github.com/en/actions/learn-github-actions/security-hardening-for-github-actions#using-third-party-actions.

We were previously using 33a6cfb after the maintainer merged my PR to allow the comment to be read from a file, there was no released version with that, but it’s now included in v2.0.0.

This will report the names of flaky tests instead of just counting them.

Bring Nomad in line with other HashiCorp projects and remove stalebot. We get
little value in cleaning up issues automatically this way, it adds extra work
for maintainers when we have issues waiting on the backlog that we intend to
do, and it presents an unkind experience to issue contributors who get their
issues closed by an impersonal bot.

Making this less specific means we can benefit from updates
to the action without needing to change the workflow, such
as the bug fix in backspace/ember-test-audit-comparison-action@a87d252,
which addresses the incorrect duration delta here:
https://github.com/hashicorp/nomad/pull/7964#issuecomment-632351171

This runs ember-test-audit for UI PRs to compare how long
the tests take for the base vs the PR. It posts or updates
a comparison of times and test count.

It’s somewhat slow to report back as it runs the test suite
three times to even out variability in a shared environment.
If we end up being unhappy with that slowness, we could try
running the repetitions in parallel as well, but that would
involve more changes to ember-test-audit.

This uses a fork of the Ember Asset Size Action to report on changes to
the filesizes of the production UI build as a comment to the PR. The
fork includes fixes to make it work with a subdirectory (ui/ in our
case) and to make it update the PR comment if it exists vs posting
repeatedly to the thread.

Add link to https://www.nomadproject.io/security.html

Also reordered the sections to put the logs at the end.