Is your feature request related to a problem? Please describe.
Related to issue #100
I am working on converting a custom Prometheus exporter made in python to using custom dynatrace extensions for ease of deployment in a net new environment. As a part of this there are several API keys/tokens and passwords that we use to access various parts of our infrastructure to gather data before applying logic and reporting metrics.

As it stands, the official documentation pages for this tool do not mention how to set up the configs for secrets. It took me several hours to find out that the documentation simply hasn't been updated in over 10 months and that there is some information on how to add the ability to have a secret in the config in this repo but not on the doc page. Specifically this page: https://dynatrace-extensions.github.io/dt-extensions-python-sdk/guides/extension_structure.html#activation-config

Where in this repo there is some small information mentioned here: https://github.com/dynatrace-extensions/dt-extensions-python-sdk/blob/main/docs/guides/extension_structure.rst#secrets

The next issue I ran into is trying to find any documentation on how to set up the activationschema.json and related files to use secrets stored in the Credential Vault in dynatrace. The only official documentation page I've found that is mildly related is marked as deprecated for 1.0 extensions. On the Credential vault page it is mentioned as a possibility here, but no specific implementation documentation exists on that page.

I also found several questions around this in the dynatrace community:
https://community.dynatrace.com/t5/Extensions/Send-a-credential-from-credential-vault-to-extension/m-p/283741
https://community.dynatrace.com/t5/Product-ideas/Extend-the-use-of-Credential-Vault-to-Dynatrace-Hub-Extension-2/idi-p/195571
https://community.dynatrace.com/t5/Extensions/Vaults-eg-Hashicorp-CyberArk-in-Dynatrace-extensions/m-p/202878

The first one m-p/283741 has a paste blob but no information on where to place it or how to change it for different credentials, like api tokens. Having this process documented will save a lot of people a lot of time.

Describe the solution you'd like

1. Fix chore - fix docs building #100
2. Update the documentation around implementing secrets to include:

• how to set up configs to pull from the credential vault
• multiple examples and a list of possible types. Ex: "referencedType": can be any of "USERNAME_PASSWORD","API_TOKEN","PASSWORD"
• how to reference those secret variables inside the python portion of the extension
• If the above extensive and explicit documentation exists elsewhere, link to it in the documentation for this tool

3. (Nice to have) Update the create command to have an example secret from the credential vault to work from.

Describe alternatives you've considered
I have spent hours going through the official dynatrace documentation, reached out to Live chat support, looked at example extensions that currently exist, and gone through community posts. All of this could have been avoided if proper documentation around this existed in one location as part of the tooling docs or on an official Dyantrace documentation guide.

Additional context
None