Added content for various auth methods + refresh README overall

[im-samz]

Looking to merge this milestone of work before the holidays.

Work done:

• Added sections for each auth type, with workflow snippets
• Organized the headings
• Made the opening paragraph more readable
• General content clean up

TODO:

• Under ##End-to-end workflows, incorporate a full workflow with comments as a visual demonstration
• Create another README for various scenarios that make use of the different Action parameters
• Uploading a new version of each workflow
• Add upload/download artifact as dependencies

Considering:

• Changing H1 title to "Deploy Project to Azure Functions"
• Instead of having all auth methods in the main README, describe just one and place instructions for the other two in a separate README.
• Reducing the table of test results
• Rewriting the ### Input parameters section in code block format to align with common practices

Tagging @ggailey777 for content review; @mattchenderson for auth review + overall feedback; @patelchandni, @ahmelsayed, @eamonoreilly for context

[im-samz]

Just merged Glenn's PR. Going to commit another round of edits. Before merging this one.

[im-samz]

@patelchandni / @eamonoreilly, could you take a look at the proposed README? I just need a reviewer to approve before I can merge this PR.

[mattchenderson]

Partial review - will continue tomorrow.

[mattchenderson]

Completing the partial review I started yesterday.