docs: Add essential docs in settings page under "URL parameters"

[ahuseyn]

Having an essential docs and explanations in the settings page would be easier for the users to understand the plugin without leaving the page as @colinmurphy suggested.

• Add usage related docs and explanations under "Available Preview URL Parameters" box
• If Faust is enabled show custom guide and alert to avoid complications. Depends on docs: Explain how to use the plugin within a Faust project #229

[colinmurphy]

@ahuseyn

Thanks for creating this. FYI added the parent for this task as #15 :)