Replace deprecated Heroku buildpack

[nickcampbell18]

remote: -----> Using buildpacks:
remote:        1. https://github.com/heroku/heroku-buildpack-static
remote:        2. heroku/nodejs
remote: -----> Static HTML app detected
remote:        ## WARNING: `heroku-buildpack-static` is deprecated
remote:
remote:        This buildpack is deprecated and is no longer being maintained.
remote:        If you are using this project, you can transition over to NGINX via an NGINX buildpack.
remote:        Use your project's existing configuration.
remote:        To find the NGINX configuration generated by the heroku-buildpack-static you can run:
remote:
remote:        ```
remote:        $ heroku run bash
remote:        ~ $ bin/config/make-config
remote:        ~ $ cat config/nginx.conf
remote:        ```
remote:
remote:        These commands will output your current NGINX config generated from your `static.json` contents.
remote:
remote:        - Write these contents to your local repo at `config/nginx.conf.erb`, commit them to git.
remote:        - Replace path logic that previously used `mruby` with static logic.
remote:        - Configure your app to use the NGINX buildpack via `heroku buildpacks:add heroku-community/nginx`.
remote:        - Remove this buildpack via `heroku buildpacks:remove heroku-community/static` (or `heroku buildpacks:remove https://github.com/heroku/heroku-buildpack-static`).
remote:
remote: -----> Installed nginx 1.21.3 to /app/bin