Improve semantic tokens for variables by splitting it up into more tokens

[rcjsuen]

RUN ${var:+word}

const lib = require("dockerfile-language-service");
const service = lib.DockerfileLanguageServiceFactory.createLanguageService();
const tokens = service.computeSemanticTokens("RUN ${var:+word}");
console.log(tokens.data.length);

10

At the moment, 10 is printed which implies there are two tokens (each taking up five numbers in the array) with the RUN instruction as one token and ${var:+word} as one token. We should split the one variable token into five separate tokens like so:

• ${var (variable)
• : (operator)
• + (modifier)
• word (parameter)
• } (variable)