Improve README for clarity, consistency, and formatting

[yfenes]

Change Summary

What and Why:

• Improve heading levels and consistency in the Readme
• Correct minor grammatical errors

How:

• Updating readme

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Documentation

• Fresh Produce
• In superfly/docs, or asked for help from docs team
• n/a

[yfenes]

I am very interested in the goals and technology of Fly, that's why I proactively created this PR and would like to know if you would consider me for this position: https://fly.io/jobs/technical-writer-devdocs/
(check the email I've sent to jobs+devdocs@fly.io for details)

I am excited to bring my skills to the project and collaborate on advancing Fly's innovative platform.

Please feel free to reach out to me at: yfenes@gmail.com.
Thank you for considering.

[andie787]

hi @yfenes
Applying in the regular way, like you did via the email address in the job description, is the best (and only!) way to start the application process.

[yfenes]

Great, thanks!