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.
