[Admin Explorer App] Add section to add, edit and delete templates

Currently we don't have an option to change the emails and issue templates, other than going directly to the table and change it raw there.

We should add a section in the admin app that takes care of this.

Depend on issue #3710

Start by reviewing the dependency in issue #3710 and the existing Admin Explorer app structure. Identify the current email and issue template data flow before scoping the new admin section. Done means administrators can add, edit, and delete both types of templates without directly changing database tables.

Written by the indexing model from the issue text.