[disma-cli] Add "init" command

[vigenere23]

Add init command to CLI for pre-creating configs and scripts with sensible defaults.

Subcommands:

• yaml : create a config.yaml config file
• json : create a config.json config file
• handlebars : create a config.template.hbs template config with a variables.yaml variables file

All subcommands should create an exec.sh script that wraps the needed bash commands for execution, like this :

guild_id=<YOUR_GUILD_ID>
# guild_id=$1  # get the first argument

disma apply -g "$guild_id" -i config.<init_extension>

If using template, should add this command before apply :

disma compile -t config.template.hbs -v variables.yaml -o config.yaml

Should maybe also create an exec.ci.sh script that uses the -f flag.