m.initialize has a bug setting the subsize if the array input is array of data views

[desean1625]

Describe the bug
m.initialize has a bug setting the subsize if the array input is array of data views

To Reproduce

data = [new DataView(new ArrayBuffer(10))];
plot.overlay_array(data);//throw "subsize must be provided with type 2000 files";

Expected behavior
The code allows arrays of Dataviews to be set and attempts to get the length for the subsize using data[0].length. However, dataviews it should be data[0].byteLength

Additional context
Fix should be

else if (Array.isArray(data) && (Array.isArray(data[0]) || ArrayBuffer.isView(data[0]))) {
            //If this is a 2-D array automatically set subsize
            hcb.type = 2000;
            hcb.subsize = ArrayBuffer.isView(data[0]) ? data[0].byteLength: data[0].length;
            hcb.size = data.length;
        }

[desean1625]

Also this needs to be corrected in bluefile.js when it flattens the 2d array

sigplot/js/bluefile.js

Line 577 in 39e66f4

length = (buf.length * buf[0].length);

[mrecachinas]

@desean1625 can you go ahead and submit a PR with these fixes?