Use placeholders for language file

[Andre601]

Right now are all messages, which have some sort of changing value in it either split up into a before and after section, or written in such a way, that the value would be at the start or end of the text.

The issue with this is, that especially for translators of the language file, there is lacking context or it's very restrictive on how you can format the text for your language. Not every language can support the syntax the current files use, so a setup with placeholders for (constantly) changing values would help a lot.
It would also reduce the amount of lines in the language file for all those strings that come before and after a value, because you now don't have to use two strings.

Example:

# Currently used setup

## single line with a value before it:
invalidName: 'is not a valid minecraft username'

## multiple lines. This case "Cooldown set to <ticks> ticks for <command?>"
cooldownSetTo: 'Cooldown set to'
ticksFor: 'ticks for'

# New setup
invalidName: '{name} is not a valid minecraft username'

cooldownSet: 'Cooldown set to {ticks} ticks for {command}'

This could help translators a lot in formatting their translation in a proper way that fits their language's speech pattern and similar.