[DOC] Add troubleshooting docs

[iameskild]

Fixes | Closes | Resolves #1036

References #1032, #1076, #1009

Please remove anything marked as optional that you don't need to fill in.
Choose one of the keywords preceding to refer to the issue this PR solves, followed by the issue number (e.g Fixes # 666).
If there is no issue, remove the line. Remove this note after reading.

Changes introduced in this PR:

• Add troubleshooting doc which outlines two common issues we've experienced when testing v0.4.0 release.
  • "DNS domain=your_qhub_domain record does not exist"
  • A Conda-Store environment fails to build

Types of changes

What types of changes does your PR introduce?

Put an x in the boxes that apply

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds a feature)
• Breaking change (fix or feature that would cause existing features to not work as expected)
• Documentation Update
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Build related changes
• Other (please describe):

Testing

Requires testing

• Yes
• No

In case you checked yes, did you write tests?

• Yes
• No

Documentation

Does your contribution include breaking changes or deprecations?
If so have you updated the documentation?

• Yes, docstrings
• Yes, main documentation
• Yes, deprecation notices

Further comments (optional)

If this is a relatively large or complex change, kick off the discussion by explaining why you chose the solution you did and what alternatives you considered and more.

[trallard]

Overall looks good - as usual, left some comments and suggestions - also pushed some minor changes so make sure to pull before making any local changes

[iameskild]

Hey @trallard, thanks for the thorough review again. I believe it's ready for a final review :)

[costrouc]

@iameskild thanks for this work. Looks great to me. I appreciate the format of the troubleshooting docs and think it makes a great template for us to use going forward for issues we are aware of but can't solve immediately.