feat(ContactForm): Share units for community library

[Aaron-Detre]

Changes

• Added buttons to library project details and project info that link to the contact form.
• Added a new issue type for sharing units.

Test w/ API

• You should only see the share unit button for units that you are an author on.
• When you click the share unit button from unit info or library project details, the contact form should automatically have sharing set as the issue type and the project set as the project.
• When the issue type is unit sharing, the summary section should be automatically filled in, and the description section should have placeholder text telling the user what kind of thing to write.

Closes #2175

[hirokiterashima]

In the Community Unit info popup, we currently say "Head to the Authoring Tool, select your unit, go to the Unit Info page, and click Publish!". Should we also mention that they can publish directly from the unit library? Something like "Click the Publish button on your unit"?

[hirokiterashima]

LGTM!

I added a minor code improvement comment inline to address.

@breity can you take a look at styling and wording?

[breity]

Looks good. 👍

I made some minor language/style updates,

[hirokiterashima]

🎉 This PR is included in version 5.186.0 🎉

The release is available on GitHub release

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