backend: add ribbons/categories endpoint

fixes #2 (closed)

backend/src/image.ts

 import {
   readAll,
   readerFromStreamReader,
-} from "https://deno.land/std@0.95.0/io/mod.ts";
+} from "https://deno.land/std@0.97.0/io/mod.ts";
 import { decode, Image } from "https://deno.land/x/jpegts@1.1/mod.ts";
 import { resize } from "https://deno.land/x/deno_image@v0.0.3/mod.ts";