Resolve "Listen on IPv6 addresses"

Closes #1

See merge request !15

Tweak README/config for prod deployment

See merge request !14

I hate the rails assets pipeline

Deployment will be done using ansible that will generate a .env file
where the database_url and secret_key_base will be defined

Update all the things

See merge request !13

Update Rails and all dependencies

See merge request !12

It addresses a Rails security issue:
https://rubyonrails.org/2022/7/12/Rails-Versions-7-0-3-1-6-1-6-1-6-0-5-1-and-5-2-8-1-have-been-released

Update README.md

See merge request !10

Upgrade Ruby, Rails and other gems

See merge request !9

Round balances

See merge request !8

12.3499999 -> 12.35

Update Rails

See merge request !7

Upgrade Ruby to 3.0.1

See merge request !6