Add missing "down" state for onClientGUIClick

[Xenius97]

Summary

This PR adds missing "down" state for onClientGUIClick (whis was unsupported previously)

Maybe this will be backward incompatible with some scripts.

Motivation

Fixes #4730

Test plan

addEventHandler( "onClientResourceStart", resourceRoot, function( )
    btnOutput = guiCreateButton(0.7, 0.1, 0.2, 0.1, "Output!", true)
    addEventHandler("onClientGUIClick", btnOutput, function(...)
        iprint(source, ...)
    end, false)

    editBox = guiCreateEdit(0.3, 0.1, 0.4, 0.1, "Type your message here!", true)
    guiEditSetMaxLength(editBox, 128)
    addEventHandler("onClientGUIClick", editBox, function(...)
        iprint(source, ...)
    end, false)
end)

bindKey("m", "down", function()
    showCursor(not isCursorShowing())
end)

Checklist

• Your code should follow the coding guidelines.
• Smaller pull requests are easier to review. If your pull request is beefy, your pull request should be reviewable commit-by-commit.

[FileEX]

Please update the wiki page

[Xenius97]

Please update the wiki page

done