doc(library/rewriter): add doxygen annotations for rewrite_* funcs
chore(.gitignore): update .gitignore
refactor(library/rewriter): move apply_rewriter_fn into rewriter.h
feat(library/rewriter): implement depth RW
refactor(library/rewriter): rename lc => ti
test(library/rewriter): add test for depth RW
test(library/rewriter): add test for depth RW