Update README.md

[andrum993]

Highlight EOL warning, tweak grammar.

[andrum993]

If my suggested IMPORTANT callout seems too strong, there's also an NOTE version - see https://docs.github.com/en/get-started/writing-on-github/getting-started-with-writing-and-formatting-on-github/basic-writing-and-formatting-syntax#alerts

[nathan-contino]

Thanks for this contribution. I made some additional wording improvements; if you accept the suggestion, I'll merge this in.

[andrum993]

Done 👍