Add `linkingId` field to the `y` channel

[etowahadams]

To address: #399

Proposal: Add linkingId field to the y channel:

Example:

"y": {"field": "peak", "type": "quantitative", "axis": "right", "linkingId": "my-ID"}

Tracks that share the same linking ID will share the same y-axis

Implementation details:

• Use valueScaleLocks in the HiGlass config to lock the y-axis together. Here is an example:

"valueScaleLocks": {
    "locksByViewUid": {
        "track1": "my-lock-group",
        "track2": "my-lock-group"
    },
    "locksDict": {
        "my-lock-group": {
            "track1": {
                "track": "track1",
                "view": "view1"
            },
            "track2": {
                "track": "track2",
                "view": "view1"
            },
            "uid": "my-lock-group"
        }
    }
},