Add FAQ page and a caution with using reserved variables

[aerorahul]

Description

This PR:

• Creates a standalone page for FAQ and Common issues
• Adds a block of caution on using variables in a users' bashrc

Fixes: #2850

Type of change

• Maintenance (documentation update)

Change characteristics

• Is this a breaking change (a change in existing functionality)? NO
• Does this change require a documentation update? NO (This is a documentation update)
• Does this change require an update to any of the following submodules? NO

How has this been tested?

Tested in PR

Checklist

• Any dependent changes have been merged and published
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• New and existing tests pass with my changes
• I have made corresponding changes to the documentation if necessary

[aerorahul]

The updated documentation can be seen at:
https://global-workflow--2898.org.readthedocs.build/en/2898/errors_faq.html#error-reserved-variables-causing-workflow-issues

[KateFriedman-NOAA]

Looks good, thanks @aerorahul !

[DavidHuber-NOAA]

Looks good!