Working Group page grammar and style fixes

[ryanmurakami]

I noticed some inconsistencies in the Working Group page and thought it would benefit from a cleanup. The focus was on making the document feel like a cohesive whole and remove discrepencies of style and structure between each section.

Here are some of the changes I made. Feedback around any of these is appreciated!

• Changed all bulleted responsibilities to start with a gerund
• Changed all references of "Node" to "Node.js"
• Capitalized all instances of "Working Group"
• Changed all instances of "WG" to "Working Group"
• Updated markdown syntax for bulleted lists to be consistent
• Language consistencies across each group
• Various grammar fixes

[williamkapke]

I REALLY like this polishing!! however, this page (as the comment in there says):

Information here should mostly mirror: https://github.com/nodejs/TSC/blob/master/WORKING_GROUPS.md

So, that document should be changed first and get approved/PRd. Any chance you're up for doing a PR to that doc?

[ryanmurakami]

@williamkapke Ah, thanks for mentioning that. Looks like there are two separate documents for top-level and core working groups. I'll make PR's for both and reference this PR in them. Thanks!

[ryanmurakami]

@williamkapke PR's complete. Also, updated the diagnostics section to match the core WG document. Looks like it actually was updated, but the site didn't stay in sync.

[ryanmurakami]

@williamkapke Both PR's for the other working group documents have been merged. You good with merging this PR?