Add PR template encouraging inline comments over normal comments

[Noratrieb]

RFC threads are known for turning into huge messes once many comments arrive. One among many reasons for this is that the comments are entirely disorganized, which makes it very hard to keep track.

I propose adding a warning the PR template that will strongly encourage people to leave inline review comments. These are significantly easier to keep track of (and can be resolved, hiding them!).

One question: who can/will approve this change? I'm just gonna go off vibes here, telling a bunch of teams about it and hoping that enough people like it that we can just ship it in and improve everyone's life!

Example (do feel free to comment normally here :D):

Important

When responding to RFCs, try to use inline review comments (it is possible to leave an inline review comment for the entire file at the top) instead of direct comments for normal comments and keep normal comments for procedural matters like starting FCPs.

This keeps the discussion more organized.

[Noratrieb]

(discuss it in https://rust-lang.zulipchat.com/#narrow/channel/122651-general/topic/encouraging.20inline.20review.20comments.20on.20RFCs)

[Lokathor]

I find inline comments harder enough to fiddle with that I deliberately just avoid them entirely.

Particularly, I don't really read the source view of an RFC, I read the rendered view and hit "back" and then there's a box to say stuff about the RFC.

Usually whatever I want to say isn't about a specific line of the text, it's about something not in the text or it's about the entire direction of th text as a whole.

Also, and this is a minor thing but it's a thing, inline comments have worse preview text when you get the notification about them.

[weihanglo]

Usually whatever I want to say isn't about a specific line of the text, it's about something not in the text or it's about the entire direction of th text as a whole.

@Lokathor Comments can be added to a file directly.

Also, and this is a minor thing but it's a thing, inline comments have worse preview text when you get the notification about them.

Agree though in general notification previews on GitHub are terrible 🤢

[Noratrieb]

I added a sentence about it

[joshtriplett]

1. I love this idea, and I'd love to see this change made.

2. Inspired by this: next time we talk with GitHub, can we make the request of having a repository where all comments in general are always in "inline" form and create threads, and support "resolve"? Effectively, make every single comment on the PR always an inline comment, even if it's not attached to a particular line or file?