Add documentation for Spring boot integration

[Quinn-With-Two-Ns]

What does this PR do?

Add documentation for Spring boot integration

https://github.com/temporalio/sdk-java/tree/master/temporal-spring-boot-autoconfigure

Notes to reviewers

[tlalfano]

There should probably be a comma or semi colon in this sentence

[tlalfano]

lgtm 👍

[tomwheeler]

I made some suggestions for improvement, most of which relate to spelling, punctuation, and style conformance.

[tomwheeler]

Suggested change

	To create an autoconfigured `WorkflowClient` all you have to do is specify some connection details in your `application.yml`.
	To create an autoconfigured `WorkflowClient`, you need only specify some connection details in your `application.yml` file.

[tomwheeler]

"specify some connection details" -- will it be obvious to the reader which ones they'll need to specify?

Looking at the application.yaml file for the basic example in samples-java, it seems that the user must specify the Namespace name and the target (endpoint address of the frontend). Perhaps it's the case that the values shown there are the defaults, but shown explicitly to make it easier for someone to change.

I would recommend that this documentation on Spring Boot provides some more guidance about what one must set, either by including it here or linking to some existing resource that already provides it.

Finally, I'll note that this section refers to an application.yml file, while the example I linked to refers to application.yaml. Maybe that doesn't matter, but I wanted to point out the discrepancy.

[tomwheeler]

UPDATE: It appears that the explanation I was looking is in the next section. In this case, consider expanding "specify some connection details in your application.yml file." to "specify some connection details in your application.yml file, as described in the next section."

[Quinn-With-Two-Ns]

Thanks, let me know how it is now