MessageTags: Add templating & edit

[Luna-devv]

• Adds a way to put one tag into another:

# set via /tags create:
haha main

sub: [insert-tag:sub]
sub2: [insert-tag:sub2]

# when being ran:
haha main

sub: hello from sub tag
sub2: even
deeper
sub cmds

• Adds a way to edit existing tags with /tags edit
• Adds a way to view the raw tag content with /tags preview raw:true
• Improves command descriptions

[Luna-devv]

Since this plugin atm uses the DataStore to store the contents of tags, vencloud does not sync those.

Would it be ok abusing the settings for storing tags to allow syncing (though this would require some migration) or is there another better solution?

An idea in Discord was to allow exporting/importing all tags as json.