Fix .com links, pulsar rebranding and rebranding readme

[Daeraxa]

Mostly this just fixes a few links:

• Org .github CONTRIBUTING.md link
• Update of .com to .dev links

However I also did a quick rebrand of the readme at the same time and I'm not sure if this is technically correct or not.

Elsewhere in the documentation we almost exclusively use pulsar -p as the "new" alias of apm.

However here it makes sense to keep the "direct" style of command in my mind. However this is where there is an issue because the binary itself is still apm.

So what I've done is change all apm instances to ppm in the style of https://github.com/pulsar-edit/pulsar/pull/273 this PR that is meant to add ppm to the PATH.

However this is also still correct if we used apm if we were talking about executing the binary directly so I don't know what the correct answer is here - feel free to make suggestions as to what we should do here. There are a lot of ppm command outputs that still talk about apm commands so whatever we choose here is also what we should be rolling out to the rest in a future pr.

[DeeDeeG]

Okay, I'm gonna merge this! Thank you so much for the effort and responsiveness to the review comments, waiting for the poll, etc!

Reasons I think this is good to merge:

• Folks in the poll on Discord unanimously approved use of a new token.
• This has my approval (figuratively + I ticked the green check mark), @confused-Techie reacted positively in the review threads, so I see at least general agreement if not multiple formal approves.
• This has a couple super important things in it, especially moving away from pulsar-edit.com URLs (see #50).

Thanks again!