[website] Add designer position page

[danilo-leal]

• I have followed (at least) the PR section of the contributing guide.

Designers out there, come in and apply! :)
https://deploy-preview-30708--material-ui.netlify.app/company/designer/

Based on https://www.notion.so/mui-org/Designer-job-ad-page-bd6818d4dd1648ac8ce3180b59eb27e0

[mui-bot]

No bundle size changes

Generated by 🚫 dangerJS against 709434f

[oliviertassinari]

We are getting closer 👍

[oliviertassinari]

It looks great, I have pushed a few polishes, I can't find anything else to improve. Maybe @mbrookes will want to have a look but not sure.

[mbrookes]

Please review suggested changes here: https://github.com/danilo-leal/material-ui/pull/1/files

[oliviertassinari]

@mbrookes I have applied suggestions on your PR to restore fixes that go introduced after you started the suggestions. Once merged, I think that we should use the new wording to update the other open roles (I have updated them to follow the same line).

[danilo-leal]

A bit off topic but for some reason, adding a : in a heading, like ### You might fit for this role if you:, fails the lint test. That's why I haven't added it.

[oliviertassinari]

for some reason

@danilo-leal I assume that it's because of https://github.com/DavidAnson/markdownlint/blob/v0.24.0/doc/Rules.md#md026---trailing-punctuation-in-heading which motivate why with https://cirosantilli.com/markdown-style-guide/#punctuation-at-the-end-of-headers. I think that we could change this header altogether if we wanted to invest more time, but it's probably fine, as is?