This commit adds a field to the GitHub issue template for a list of the
plugins that are installed on the Elasticsearch installation. This is a
common enough ask that it is better to just collect this information up
front.
Relates #19840
This commit adds a note to the GitHub issue template noting that bug
reports on OS that we do not support or feature requests for OS that we
do not support will be closed.
Relates #19322
This commits adds an issue template for contributors that open bug
reports or feature requests.
Additionally, this commit adds a .github subdirectory to the project and
moves the CONTRIBUTING.md file to that directory.
Closes#16773