Templates: embed the templates in-binary

Rocket's templating is not exactly friendly when it comes to embedding
in-binary. Rocket's template fairing requires a `template_dir` directory
pointing to the directory containing templates.
A quick workaround to this would be to have custom fairings with
`template_dir` merged with the value `.`
But in bare-metal scenarios like what docker's scratch image mimics, we
don't exactly have a '.' file, so instead for this very project, I have
to point the `template_dir` to the `upload` folder, which is created by
`bin` on execution. Checkout the Dockerfile for more info

Signed-off-by: Gunwant Jain <mail@wantguns.dev>

docker-compose.yml

@@ -4,9 +4,9 @@ services:
     image: wantguns/bin
     container_name: pastebin
     ports:
-      - 127.0.0.1:6162:6162
+      - 127.0.0.1:6163:6163
     environment:
-      - ROCKET_PORT=6162
-      - ROCKET_LIMITS={form="16 MiB"}
+      - BIN_PORT=6163
+      - BIN_LIMITS={form="16 MiB"}
     volumes:
-      - ./upload:/app/upload  # upload folder will have your pastes
+      - ./upload:/upload  # upload folder will have your pastes