Improve documentation of the crate

[DDtKey]

We need to enrich the crate with documentation

Depends on #1

### Tasks
- [x] Contribution guide - @ubiratansoares is assigned
- [x] Improve crate-level documentation (docs.rs)
- [ ] Document usage of each existing module
- [x] Align readme with documentation
- [x] New issue template
- [x] Activate `#![deny(missing_docs)]` at crate level to avoid missing documentation

[ghost]

Anything I can do to help?

[DDtKey]

Two remaining tasks are:

• Document usage of each existing module We have a number of modules which has been moved from testcontainers repo, most of them don't have a documentation. Need to actualize and write a documentation like this: https://github.com/testcontainers/testcontainers-rs-modules-community/blob/6a4d10acbedd19f54a505afd09b66343744b4a64/src/rabbitmq/mod.rs#L6-L29

• Contribution guide

I would be glad for any help

[ghost]

Okay I'll have a go at adding documentation for the use of each module and submit a PR.

[ubiratansoares]

@DDtKey Is there anyone assigned to Contribution Guidelines? If not, I'd love helping with that! 🙂

[DDtKey]

No, feel free to take on this task! Thank you!🙏

[DDtKey]

To actualize the state: We still need to cover undocumented modules. But there is no need to document all of them at once.

I'm happy to accept PRs with documentation for 1 module at a time.