Command for adding crash report to issue description

[Marcono1234]

The Problem

Once #627 has been merged there will be cases in which Arisa won't add a crash report snippet to the issue description, this includes:

• Existing crash reports which have been attached before the module has been activated
• Multiple crash reports have been attached by the reporter
• Crash reports attached by users other than the reporter
• The issue description already contains a crash report snippet

For these cases it would be useful to have a command for manually updating the description with the snippet from a crash report attachment. The format of the {code} block being added should use the same format as #627 to make sure Arisa recognizes it, and to get consistent results.

Possible Solution

Add a $ARISA_INCLUDE_CRASH <attachment-name> (or similar) command; the command should be usable by Helper+.
It should:

• Check if an attachment with the specified name exists and verify that it is a Minecraft crash report
• NOT check whether the description already contains a crash report snippet. Adding a snippet should be possible even if the description already contains one.
• Use the same snippet format as Update description with crash #627