Add socials to README

[Dedalo314]

The socials include: Discord, X and DockerHub.

What does this PR do?

Adds GPTStonks' socials to README:

• X badge.
• Discord badge.
• DockerHub badge.

Before submitting

• Did you make sure title is self-explanatory and the description concisely explains the PR?
• Did you make sure your PR does only one thing, instead of bundling different changes together?
• Did you list all the breaking changes introduced by this pull request?
• Did you test your PR locally with pytest command?
• Did you run pre-commit hooks with pre-commit run -a command?

Did you have fun?

Make sure you had fun coding 🙃