Add .cake extension to supported debug file types

[Redth]

Currently, trying to debug Cake.exe while executing .cake script files will not hit any breakpoints set inside of VS Code since the file type is not supported.

Adding the file extension .cake to this list of supported extensions allows us to launch Cake.exe with the mono soft debugger, and subsequently attach to it with this extension to debug our cake scripts.

Here's a screenshot of a cake script with breakpoints working after this change:

Finally, here's how we're launching and attaching via cake if anyone's interested in seeing it:

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "StartCake",
            "type": "mono",
            "request": "launch",
            "program": "${workspaceRoot}/tools/Cake/Cake.exe",
            "runtimeArgs": [
                "--debug",
                "--debugger-agent=transport=dt_socket,server=y,address=127.0.0.1:55556"
            ],
            "args": [
                "${workspaceRoot}/build.cake",
                "--verbosity=diagnostic",
                "--debug"
            ],
            "cwd": "${workspaceRoot}",
            "console":"internalConsole",
            "noDebug": true
        },
       {
            "name": "AttachCake",
            "type": "mono",
            "request": "attach",
            "address": "localhost",
            "port": 55556
        }
    ],
     "compounds": [
        {
            "name": "DebugCake",
            "configurations": ["StartCake", "AttachCake"]
        }
    ]
}

[weinand]

Thanks a lot for the PR!