Add kate to editors list

[larskanis]

This adds some notes, how to setup the kate editor with ruby-lsp.

Motivation

I couldn't find any information how to setup kate with ruby-lsp by google search or by inspecting ruby-lsp or kate resources.

Implementation

The config JSON is taken from the solargraph default setting of kate and adjusted to use ruby-lsp.

Automated Tests

None - the change is just documentation.

Manual Tests

I checked that the following actions work in kate:

• go to definition
• search references
• hover over classes and methods to see documentation
• extend selection, shrink selection
• document outline shows the methods

[larskanis]

I have signed the CLA!

[st0012]

Thanks! Can you also update the editors list at the top of the file?

[andyw8]

For reference, here is the current config:

https://github.com/KDE/kate/blob/9e4ecb181c592a8cffdac0c66a0f3b3ebb4ac49a/addons/lspclient/settings.json#L237-L242

        "ruby": {
            "command": ["solargraph", "stdio"],
            "rootIndicationFileNames": ["Gemfile", "Gemfile.lock", "gems.rb", "gems.lock", "Rakefile"],
            "url": "https://solargraph.org",
            "highlightingModeRegex": "^Ruby$"
        },

[vinistock]

Thank you for the contribution!