Rename ISSUE_TEMPLATE/config.yaml to config.yml

Issue template configuration is the only github configuration file I've found which does not support both `*.yaml` and `*.yml` extensions. Drat.

Add link to feedback portal

Provide a link to feedback.secondlife.com from the issue creation page.

build.yaml: Build shared branches

We're currently building every single commit pushed to Github. This is
racking up $20k in build charges a month and is generally superfluous.

This changeset alters build triggers so that builds automatically run if
they are committed to a **shared branch**:

- `release/*` - A release stabilization branch
- `project/*` - A project viewer branch
- `main/*` - The default/stable branch

PR commits are also automatically built.

...need to build another commit? Developers can trigger one using a
manual workflow run.

Update enhancement.md

Update bug.yaml

Add a basic CONTRIBUTING.md

Issue templates

Provide basic instructions in-repository for contributing to Second
Life.

This avoids the need for a separate job step.

When a PR appears on the QA board, QA wants to know whose team it came from.
So every PR on the viewer repo should be labeled with team:viewer.

following promotion of DRTVWR-596