fixed typo in developer-docs

[ktsrivastava29]

Fixes #issue-number

I have verified that this pull request:

• [x] has no linting errors (npm run lint)
• [x] is from a uniquely-named feature branch and has been rebased on top of the latest develop branch. (If I was asked to make more changes, I have made sure to rebase onto develop then too)
• [x] is descriptively named and links to an issue number, i.e. Fixes #123

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• p5.js-web-editor
  • app-ted2d6c-p5-js-web-editor.rls.sh
  • preview-ted2d6c-p5-js-web-editor.rls.sh

:wrench:Environment Status : https://app.releasehub.com/public/Processing%20Foundation/env-bccf9ff72b

[ktsrivastava29]

Many of the .md files in the developer documents folder had punctuation and grammatical errors, which I've fixed. Please review the changes; if any modification is required, I'll be pleased to make them.