[BetterCodeBlocks] Alias c++ to cpp

[leumasme]

"cpp" is a supported codeblock language in the plugin, but "c++" does not get recognized. Discord desktop supports "c++".
If non-alphabetic characters for the language specifier are already handled fine, this should be as easy as adding an extra case here
https://github.com/Juby210/Aliucord-plugins/blob/main/BetterCodeBlocks/src/main/java/io/github/juby210/acplugins/bettercodeblocks/GrammarLocatorImpl.java#L40-L45