docs: clean up README examples

[shadowspawn]

• remove option overwrites from repeated options (#14)
• remove array for plain values (#19)
• flags for flags, values for values (#19)

If this is acceptable, happy to update the code to behave accordingly.

[shadowspawn]

Did you consider generating these docs?

Not yet. The docs got written first, and guided the initial implementation. I am proposing changes to README, then will update code to match. 😄

[shadowspawn]

(Deleted my comment with code which included multiple changes not all related to this PR.)