support user setting for PlantUML style to use

[MinnieTheMoocher]

when invoking the plantuml.jar, it understands the option
-config myfile.txt
, where "myfile.txt" is a simple text file inside which you can specify your desired default style to be used.

For example, this would be a valid input:

skinparam BackgroundColor    transparent

skinparam DefaultFontSize    11
skinparam DefaultFontName    Arial

skinparam class {
   ArrowColor                #00509B
   BorderColor               #00509B
}

I would like to request that I can configure the path to such a file in the VSCode user settings,
for example like this:

"plantuml.style": "C:\\some\\folder\\somefile.txt"