Doc browser homepage update

[hwahlstrom]

Purpose

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

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

FYIs

@Amoursol

[QilongTang]

@hwahlstrom Would you provide a screen shot of the UX diff?

[hwahlstrom]

@hwahlstrom Would you provide a screen shot of the UX diff?

Done!