Improve command syntax

[moxvallix]

Implement command literals with backticks, replacing the existing forward slash method. This allows for commands to be written across multiple lines, and fixes a bunch of syntax incompatibilities.

# Old syntax
/data modify storage foo:bar baz set value true

# New syntax
`data modify storage foo:bar baz set value true`

## Allows for multi-line commands
`
	execute
		as @a[type=minecraft:zombie]
		at @s
		positioned ~ ~1 ~
		run &{particles()}
`