feat: Add settings module for environment variable

[xmnlab]

Description

This PR aims to add a configuration mechanism that will allow us to use epigraphhubpy with local databases.

Additionally, this PR proposes to:

• remove greetings gh actions workflow. we have already PR and Issue template, so we don't need it
• move gh actions release step to its own gh actions workflow. also it was improved in order to publish the package to pypi
• add a postgresql service for the CI, so we can test the new configuration mechanism
• refactor the makefile. some targets were grouped and others removed

Related Issue

Checklist

• [x] I've read the CODE_OF_CONDUCT.md document.
• [x] I've read the CONTRIBUTING.md guide.
• [x] I've used pre-commit hook locally.
• [x] I've written tests for all new methods and classes that I created.
• [x] I've written the docstring in Google format for all the methods and classes that I used.
• [x] Semantic-release prefix title used:
  • Use the prefix chore(docs): for Examples / docs / tutorials / dependencies update
  • Use the prefix fix: for a bug fix (non-breaking change which fixes an issue).
  • Use the prefix chore(improvement): for an improvement (non-breaking change which improves an existing feature).
  • Use the prefix feat: for a new feature (non-breaking change which adds functionality).
  • Use the prefix breaking change: for a breaking change (fix or feature that would cause existing functionality to change).
  • Use the prefix chore(security): for a security fix.

Note: The title prefix can be also expanded with more information inside the parenthesis. Some examples for a full title (prefix + message):

• fix(login): Fix the login page.
• feat(forecast): Add a weather forecast page.
• chore(security-login): Add a weather forecast page.

[xmnlab]

@fccoelho @eduardocorrearaujo this PR is ready for review. I hope that the CI will work now, otherwise I will take a look into that later.

@esloch @luabida also, if you have time for review this PR, that would be great.

thanks!

[xmnlab]

@fccoelho thank you so much for your review, really appreciate that :) If you want we could have a quick call this week to discuss these points!

thank you!

[xmnlab]

as it was already approved, I will move it forward and merge it! thanks @fccoelho and @luabida for the review!

the current PR is failing now just because we hit the limit for the gtrends tests: https://github.com/thegraphnetwork/epigraphhub_py/pull/169/checks#step:8:92