[mabidakun]

What does this PR do?

• Problem: README.md had 19 markdownlint issues: indented list items, missing blank lines around lists and code blocks, double blank lines, trailing spaces, a heading that ends with a colon and code blocks with no language.
• This PR: fixes all of them. List items start at the left margin, blank lines and trailing spaces are tidied, "Usage:" becomes "Usage", and each code block has a language (text for the example file, swift for code), so GitHub highlights the Swift examples.
• Risk: none. Formatting only; the text does not change. The Swift examples now have syntax highlighting, and the "Usage" heading keeps its #usage anchor.

Test Evidence

Run locally on 67ea0db:

Check	Command	Result
Markdown lint	npx markdownlint-cli@0.49.1 README.md	no issues (19 on main)