feat: URL sharing of viewer state

[ShrimpCryptid]

Part 3/4(?) for #107! Implements sharing + loading for the channel and viewer states via URL. Users can now click the Share button to get a long link containing most of encoded viewer state.

The viewer state is still missing serialization + deserialization of the control points for channels, which will come in hopefully one last final PR.

Estimated review size: Small, 15 minutes. Please turn off whitespace

Changes

• Restructures AppWrapper to allow the share modal to gain access to the viewer state context.
• The share modal now includes the viewer state serialized to parameters.
• Viewer state can now be loaded in via the URL on startup.
• Moved modals to the components/Modals folder.

Validation

1. Clone and run the branch locally.
2. Open this link. You should see a view that resembles the picture below: http://localhost:9020/viewer?mode=volumetric&mask=0&image=cell&axes=1&bb=1&bbcol=ff0000&bgcol=511717&rot=1&bright=100&dens=4.939266903149523&interp=1&reg=0%3A0.7214076246334311%2C0.2363013698630137%3A1%2C0.2894736842105263%3A0.8157894736842105&slice=0.5%2C0.5%2C0.5&lvl=83.24250241857466%2C154.03418252176715%2C255&t=0&view=3D&c0=ven%3A1%2Csen%3A0%2Cisv%3A128%2Cisa%3A1%2Cclz%3A0%2Ccza%3A1%2Ccol%3Aed8f17&c1=ven%3A1%2Csen%3A0%2Cisv%3A128%2Cisa%3A1%2Cclz%3A0%2Ccza%3A1%2Ccol%3Ae4ffc6&c2=ven%3A1%2Csen%3A0%2Cisv%3A128%2Cisa%3A1%2Cclz%3A0%2Ccza%3A1%2Ccol%3A8da3c0&c3=ven%3A0%2Csen%3A0%2Cisv%3A128%2Cisa%3A1%2Cclz%3A0%2Ccza%3A1%2Ccol%3Af5f1cb&c4=ven%3A0%2Csen%3A0%2Cisv%3A128%2Cisa%3A1%2Cclz%3A0%2Ccza%3A1%2Ccol%3Ae0e3d1&c5=ven%3A0%2Csen%3A0%2Cisv%3A128%2Cisa%3A1%2Cclz%3A0%2Ccza%3A1%2Ccol%3Add9bf5&c6=ven%3A0%2Csen%3A0%2Cisv%3A128%2Cisa%3A1%2Cclz%3A0%2Ccza%3A1%2Ccol%3Ae3f4f5&c7=ven%3A0%2Csen%3A0%2Cisv%3A128%2Cisa%3A1%2Cclz%3A0%2Ccza%3A1%2Ccol%3Aff6200&c8=ven%3A0%2Csen%3A0%2Cisv%3A128%2Cisa%3A1%2Cclz%3A0%2Ccza%3A1%2Ccol%3Af7db78&url=https%253A%252F%252Fs3-us-west-2.amazonaws.com%252Fbisque.allencell.org%252Fv1.4.0%252FCell-Viewer_Thumbnails%252FAICS-22%252FAICS-22_8319_2025_atlas.json

Discussion questions:

• Should we only save channel or viewer states that deviate from the default? That would shorten the URL by a lot. (Though it raises the question of whether we'll be changing the defaults in the future!)