patch: Added Gemini Extension and CLI Support in README

[christian-kreuzberger-dtx]

Adding Gemini CLI Support

to try it out:

Setup Gemini CLI First (btw, you'll need a google account)

# install it
npm install -g @google/gemini-cli

Install the extension (I did it locally, but the plan is to use the github.com URL in the end)

gemini extensions install --path ../dynatrace-mcp/

This should output something like

Extension "dynatrace-mcp-server" installed successfully and enabled.

Configure it:

export DT_PLATFORM_TOKEN=...
export DT_ENVIRONMENT=...

Now check if the extension is available

gemini mcp list

In theory, you should be able to start gemini, and use the tools:

gemini
# in gemini
Which Dynatrace environment am I connected to?

[krisdyna]

looks good. lets merge