Refactor and modularize `processSection.js`

[rexagod]

This has been marked as a good candidate for becoming a first-timers-only issue like these, meaning that it's simple, self-contained, and with some extra formatting, could be a great entry point for a new contributor. If you're familiar enough with this code, please consider reformatting or reposting it as a first-timers-only issue, and then ping @jywarren to get it labelled. Or, if this is not your first time, try to solve it yourself!

To complete this PR, we want you to convert processSection.js into smaller modules and then make use of those inside it. We'd also like if you could, along the way make some refactors such as reducing the numbers of params passed to a function by encapsulating them into an object
with similar props and accessing it accordingly. A good place to start doing this is

inline-markdown-editor/src/processSection.js

Lines 64 to 65 in c634253

	// we should need fewer things here:
	o.onComplete(xhr.status, after, html, _el, uniqueId, __form, o);

Also, please don't hesitate to ping me, or @jywarren to help you if you're stuck anywhere!

Thanks! 🎉

[aditi5050]

Hello, @rexagod I would like to work on this issue can you please assign this to me.