Updating doc browser NoContent page

[hwahlstrom]

Removing unnecessary CSS

Purpose

Replacing content on the Documentation Browser homepage (or No Content page) to more accurately describe what users can find there.

Removing unnecessary CSS.

Declarations

Check these if you believe they are true

• The codebase is in a better state after this PR
• Is documented according to the standards
• The level of testing this PR includes is appropriate
• User facing strings, if any, are extracted into *.resx files
• All tests pass using the self-service CI.
• Snapshot of UI changes, if any.
• Changes to the API follow Semantic Versioning and are documented in the API Changes document.
• This PR modifies some build requirements and the readme is updated

Release Notes

Updated the Documentation Browser homepage to include a description about the types of content that can be found there: node information, issue documentation, and information about settings.

Reviewers

@QilongTang