Install patched custom django-raster version via pyproject.toml (used py poetry)

[4lm]

Hi @henhuy,

I have a PR in which I move the installation of your patched django-raster version (also see #15) into the pyproject.toml.

This was needed for all users who want to install locally via poetry (without Docker, as recommended in readme).

I also removed the extra step in local and production Dockerfiles.

Edit: I tested it with docker-compose -f local.yml up -d --build. Build process runs smooth. Didn't test it with production.yml (lack of production config), but I strongly assume that it will be OK too and would risk merging it.

Please review and merge, if you like what you see.

[4lm]

@henhuy, this PR has to be merged in order for the my, in the readme, described install to work!

I know, you didn't merge it, because you are not sure if this works in production with Docker. I'm quite sure it works and would just merge it and fix later in the unlikely event that it breaks the production build (I mean, we are not in production yet, so who cares anyways)!

But in case if you insist on testing this specific detail first - can you maybe test it (build and run production Docker). Do you have a production config (I don't have one)? If you don't have time and won't merge without a production test first, please let me know, then I will create a production config and do a production test!

[henhuy]

Let's be crazy and merge it! ;)