GitHub Integration - Create link to public url for issue

### Problem Statement

When viewing an Issue and leveraging the (modern) GitHub Integration to Create an Issue, the resulting URL is a private link to the Issue, which is wonderful.

However, for applications that develop in the open source, the resulting URL is not viewable, since it's not shared "publicly".
[example](https://github.com/pypi/warehouse/issues/13978).

This prevents any potential contributors that have not been invited into the Sentry org to view any further details about the error, and potentially help to resolve.

Individually clicking "Share" and copying the public link works, but is a cumbersome workflow.

### Solution Brainstorm

I'd like some sort of configuration toggle for the GitHub Integration Configuration entry to toggle "Share publicly by default" for a configured repository, so that when I Create/Link a GitHub Issue, the resulting URL is shared publicly by default.

Probably not applicable globally, but only repos that are public.

Maybe instead of a repo-based config, an individual toggle on the Create/Link page that allows the user to click "Share" in that context? I don't know.

### Product Area

Settings - Integrations