Add Discord icon to Inkeep box on docs

[hcourdent]

The idea is that some users stop their journey after asking AI about something, and they might get frustrated if we don't have yet the docs or the feature they are looking for. But we would very much like those users to ask on Discord and engage in a talk.

Like this:

The way to do this today is via "aiChatSettings.getHelpCallToActions", for you it would look like:

   getHelpCallToActions: [
        {
            name: "Ask on Discord",
            url: "https://discord.com/invite/V7PM2YHsPB",
            icon: {
                builtIn: "FaDiscord"
            }
        },
        {
            name: "File an Issue",
            url: "https://github.com/windmill-labs/windmill/issues",
            icon: {
                builtIn: "FaGithub"
            }
        }
    ],

This will add a "Get help" button on the bottom right of the AI chat.