docs(java): add section about spring boot

[azdanov]

📑 Description

Added a section on how to add spring-boot support to the pack.

ℹ Additional Information

[github-actions]

Review Checklist

Does this PR follow the [Contribution Guidelines](development guidelines)? Following is a partial checklist:

Proper conventional commit scoping:

• If you are adding a new plugin, the scope would be the name of the category it is being added into. ex. feat(utility): added noice.nvim plugin

• If you are modifying a pre-existing plugin or pack, the scope would be the name of the plugin folder. ex. fix(noice-nvim): fix LSP handler error

• Pull request title has the appropriate conventional commit type and scope where the scope is the name of the pre-existing directory in the project as described above

• README is properly formatted and uses fenced in links with <url> unless they are inside a [title](url)

• Entry returns a single plugin spec with the new plugin as the only top level spec (not applicable for recipes or packs).

• Proper usage of opts table rather than setting things up with the config function.

• Proper usage of specs table for all specs that are not dependencies of a given plugin (not applicable for recipes or packs).

[Copilot]

Pull Request Overview

Adds documentation for enabling Spring Boot support in the Java community pack.

• Introduces a new "Spring Boot" section with a sample Lua plugin configuration.
• Notes the need to install the spring-boot-tools extension.

[Uzaaft]

Cant this be a seperate pack?

[azdanov]

Cant this be a seperate pack?

Yeah I think so. It does need jdtls to work, but otherwise could be useful as a separate one.