Add terminating newline to generated tsconfig.json

This commit adds a terminating newline to tsconfig.json
generated by `tsc --init`, just like `npm init`'s package.json.

The main reason I created this pull request is for editor friendliness.
Recently I created a new TypeScript project with `tsc --init`,
then I modified some compilerOptions and tried to git-commit the change,
but I found a newline was automatically added by my editor.

I think it's better that the default tsconfig.json template has a
terminating newline.

src/compiler/commandLineParser.ts

@@ -1893,7 +1893,7 @@ namespace ts {
             }
             result.push(`}`);
 
-            return result.join(newLine);
+            return result.join(newLine) + newLine;
         }
     }