update to latest tjfs-core and get build working again

[jebeck]

Cf. discussion in #76, this is a start at getting tfjs-tsne working with the latest tfjs-core. (At @stitchfix, we really want the Web Worker & OffscreenCanvas support that's now in tfjs-core!)

This branch successfully builds the library (with some hacks like the tsconfig.json change to suppressImplicitAnyIndexErrors 👀 ), but when I link it into a consuming app I get the same error reported in #77: "Failed to link vertex and fragment shaders"

Perhaps this branch can be a jumping off point for someone who knows the tfjs-core API better than I do? (Which is not at all!)

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This change is 

[Fil]

Same error reported in #55 #62 #81.

[Nicola17]

I've been out of the loop of the new tfjs-core, @tafsiri can you or someone else have a look into this?