Feature: add link to 10x Projects board on Github

[jonadecker]

Is your feature request related to a problem? Please describe. We need a go-to location for interested folks to find the 10x Projects Board

Describe the solution you'd like We've discussed adding it to the site header and are inspired by the way USWDS links to their Github Repo in the header > site utilities area

Describe alternatives you've considered Besides the site header, we've considered it as an addition to the About side nav (with different treatment since it is an external link, so hard coding it into the nav doesn't seem like the right approach from a design pattern/best practices standpoint) or perhaps under Investments. But because Investments doesn't have a side nav, this seems problematic and would require more involved design considerations.

There's been some discussion about adding it to the global nav, but again, linking to an external resource from the global nav doesn't seem like a good practice.

Additional context We do want to identify opportunities within the site content to link to the project board, but we want it to be easily discoverable. We don't want to have to give folks navigation directions to find the link!

There is also an opportunity to share specific investment portfolio views within each Investment area

### Tasks
- [ ] Meghan does some things
- [ ] Design options
- [ ] Review options with team
- [ ] Review items with stakeholders
- [ ] Decide on approach
- [ ] Implement approach
- [ ] Test and remediate

[maomeara63]

ACCEPTANCE CRITERIA

• [ ] GH Project link is prominent easy to find
• [ ] Link copy is easy to understand
• [ ] Rationale about whether to include the GH icon
• [ ] Additional in-page (in-copy) link opportunities are identified and copy written