feat: execute service as distributed erlang (#96)

To create a cluster with distributed nodes, the following changes were made:

* Use [`dns_cluster`][0] to execute distributed nodes
* Add _script_ to execute distributed nodes locally

Also, improve local execution by:

* Use [`mix release`][1] to make easier [deploy `phoenix`][2]
* Use [`compose watch`][3] to synchronize code from the host with the service

Some minor improvements:

* Ignore files and folders in git and docker
* Remove boilerplate comments

[0]: https://github.com/phoenixframework/dns_cluster
[1]: https://hexdocs.pm/mix/Mix.Tasks.Release.html
[2]: https://hexdocs.pm/phoenix/releases.html
[3]: https://docs.docker.com/compose/how-tos/file-watch/

Co-authored-by: Joao P Dubas <joao.dubas@gmail.com>
Reviewed-on: #96
Co-authored-by: Joao P Dubas <joao.dubas+gitea@gmail.com>
Co-committed-by: Joao P Dubas <joao.dubas+gitea@gmail.com>

.dockerignore

@@ -0,0 +1,33 @@
+.dockerignore
+docker-compose.yml
+docker-compose.*.yml
+
+# Ignore git, but keep git HEAD and refs to access current commit hash if needed:
+#
+# $ cat .git/HEAD | awk '{print ".git/"$2}' | xargs cat
+# d0b8727759e1e0e7aa3d41707d12376e373d5ecc
+.git
+!.git/HEAD
+!.git/refs
+
+# Common development/test artifacts
+/cover/
+/doc/
+/test/
+/tmp/
+/.elixir_ls
+/.elixir-tools/
+
+# Mix artifacts
+/_build/
+/deps/
+*.ez
+
+# Generated on crash by the VM
+erl_crash.dump
+
+# Static artifacts - These should be fetched and built inside the Docker image
+/assets/node_modules/
+/priv/plts/
+/priv/static/assets/
+/priv/static/cache_manifest.json