Change "Openings" to "Help Wanted"

[TheGlitch76]

We don't want to push joining a team as the primary way to contribute to Quilt. It's not necessary, and we expect people to contribute some before joining a team, the opposite of what parts of the website currently suggest.

This PR changes the "Openings" page to a "Help Wanted" page that is hopefully much less intimidating (it only asks for contribution, not accepting responsibility) and more reflective of how contributing to Quilt actually works.

Reviews and rewording is always welcome.

TODO before merge:

• [ ] Add a redirect from "openings" to "help-wanted" (I don't know how to do this)
• [ ] Re-do the section on Build Tools

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[obj-obj]

You should be able to make a redirect by making a page at the old location and doing this:

---
import Redirect from "@layouts/Redirect.astro";
---

<Redirect href="new-url" />

[EnnuiL]

It appears that this PR stalled, which worries me; I consider it a prerequisite for PR #90

[gdude2002]

Looks like a bad merge was pushed to common.flt, this is going to need fixing pretty quickly

[Southpaw1496]

Oops. I did check and everything looks fine, but I wasn't really sure if there were any auditing steps to run.

[gdude2002]

No, you don't get me - you committed a merge conflict without resolving it.