[docs] Need documentation for Java SDK

[hhunter-ms]

Java SDK is available to use, but there is no documentation for it.
Use documentation in dapr-sandbox/components-dotnet-sdk as model.
I can support.

@tmacam

Related docs issue: dapr/docs#3189

[hhunter-ms]

@tmacam feel free to self-assign or assign to someone else! and let me know if or how I can help

[tmacam]

I will be able to pick this up by EOW.

[hhunter-ms]

@tmacam with 1.11 release wrapping up, do you think you'll be able to work on this? or know of someone who can?