Improve on type formatting so it does not return unnecessary edits

[rcjsuen]

As the second line already has a tab there, we should not be replacing a tab with a tab.

const library = require("dockerfile-language-service");
const service = library.DockerfileLanguageServiceFactory.createLanguageService();
const edits = service.formatOnType(
    "EXPOSE 8081 \n\t8082",
    {line: 0, position: 11},
    "\\",
    {
        insertSpaces: false,
        tabSize: 4
    }
);
console.log(edits[0]);

{
  range: { start: { line: 1, character: 0 }, end: { line: 1, character: 1 } },
  newText: '\t'
}