Documentation suggestions

[tcobbs-bentley]

Note: I could create separate issues for everything below, but I feel that it will be easier for whoever makes the updates to just fix all of them at once.

While using viewer for the first time, I ran into a number of documentation issues as well as having a number of changes I would like to suggest:

Main Repository

README.md

• I feel it should update to point to project READMEs after templates are used to create projects. The current instructions imply that you can just run the command immediately after checkout, and that's not the case.
• The main README.md says to use pnpm while web and desktop README.md files say to use npm. We should choose one. (I think both work.)

Web Client

README.md

• The "test client" link broken
• I feel that sample redirect URLs should be provided so that users at least have valid ones they can use.
• The "generate a test iModel" link broken

Desktop Client

README.md

• The sample redirect URI should be enclosed in backticks (`) so that it doesn't become a link.