Update page names to match URL slug

Background/context Currently, our page names don't match the URL slug for each page. This is potentially confusing for humans reading about azd and is not optimized for search engines to use the HTML tag structure to crawl our site and index it properly.

We want to update the URL slugs for the pages, then create a 301 permanent redirect from the current URL slug to the new one.

Main Pages

Page Name	Current URL Slug	Change to
Getting Started	/about	/getting-started
Contribute	/docs/intro	/ contribute

FAQ Pages

Page Name	Current URL Slug	Change to
What is "azd"?	/docs/faq/azd	/docs/faq/what-is-azd
What is "azd-template"?	/docs/faq/azd-template	/docs/faq/what-is-an-azd-template
How do I use azd-template?	/docs/faq/use-azd-template	/docs/faq/how-to-use-azd-templates
How do I discover one?	/docs/faq/discover-azd	no change
How do I create templates?	/docs/faq/create-template	no change
How do I contribute templates?	/docs/faq/contribute-template	no change
How are templates rated?	/docs/faq/rate-template	no change
How do I request templates?	/docs/faq/request-template	/docs/faq/request-a-template

Link to Learn Docs

No changes.

Submit your template! Button

Currently the Submit your template! button links to /awesome-azd/docs/intro/ With these changes, we'll want the button to link to the Contributor Guide (same as today) and it's new URL slug: /contribute

### Tasks
- [ ] Update main page URL slugs
- [ ] Update faq page URL slugs
- [ ] Create an HTTP `301` redirect for the changed pages and retired URLs
- [ ] Update the link to the `Submit your template! button

Azure / awesome-azd