enable keychords of 3 or more steps - BRIEF Keymap usecase.

[AaronNGray]

This is an extension of the issue enable keychords of 3 or more steps #6966 for the usecase of a BRIEF (Basic Reconfiguable In teractive Editting Facility) Editor Key Emulation.

For this there is a need to be able to execute Chord keystroke commands immediately at each step if so desired.

with the Home and END keys, first HOME to goto the beginning of the line, HOME HOME to the top of the current window, then HOME HOME HOME to goto the top of the document. END behaves simularly, end of line, bottom of window, and end of document.

For this I am proposing the following simple flag immediate: true, this executes each command immediately and still continues to for a chord where valid.

keymap example :-

    {
        "key": "home",
        "command": "extension.brief.cursorBeginningOfLine",
        "immediate": true,
        "when": "editorTextFocus"
    },
    {
        "key": "home home",
        "command": "extension.brief.cursorTopOfViewport",
        "immediate": true,
        "when": "editorTextFocus"
    },
    {
        "key": "home home home",
        "command": "extension.brief.cursorBeginningOfDocument",
        "immediate": true,
        "when": "editorTextFocus"
    },
    {
        "key": "end",
        "command": "extension.brief.cursorEndOfLine",
        "immediate": true,
        "when": "editorTextFocus"
    },
    {
        "key": "end end",
        "command": "extension.brief.cursorBottomOfViewport",
        "immediate": true,
        "when": "editorTextFocus"
    },
    {
        "key": "end end end",
        "command": "extension.brief.cursorEndOfDocument",
        "immediate": true,
        "when": "editorTextFocus"
    }