The `error-report` label was not being added to error reports
submitted by panics in the web player, despite the `labels` query
parameter in the URL. Users do not have triage/write access to the
repo, which is required by GitHub to add a label to an issue.
Add an issue template for error reports with the `error-report`
label. This template is now added to the issue URL, which
automatically adds the tag regardless of access level.
Mike Welsh