docs: update README and fix code some commentary typos

[anonhostpi]

Update doc to include default value for relative-redirect-url

Based on:

oauth2-proxy/pkg/apis/options/options.go

Line 123 in fc701bf

flagSet.Bool("relative-redirect-url", false, "allow relative OAuth Redirect URL.")

Description

Update doc to reflect this line of code:

oauth2-proxy/pkg/apis/options/options.go

Line 123 in fc701bf

flagSet.Bool("relative-redirect-url", false, "allow relative OAuth Redirect URL.")

Motivation and Context

I am scrubbing through the source code and documentation to learn how OAuth2-Proxy works internally, as a way for me to learn how each of the configs work in detail.

Since, I am already digging into each in detail, I might as well share any discrepancies I find.

How Has This Been Tested?

N/A

Checklist:

• My change requires a change to the documentation or CHANGELOG.
• I have updated the documentation/CHANGELOG accordingly.
• (N/A) I have created a feature (non-master) branch for my PR.
• (N/A) I have written tests for my code changes.