Elliptic vulnerability - bump to >= 6.5.7

[elgreg]

Is your feature request related to a problem? Please describe.

Snyk found multiple vulns in Elliptic.

In the Elliptic package 6.5.6 for Node.js, EDDSA signature malleability occurs because there is a missing signature length check, and thus zero-valued bytes can be removed or appended.

In the Elliptic package 6.5.6 for Node.js, ECDSA signature malleability occurs because there is a missing check for whether the leading bit of r and s is zero.

In the Elliptic package 6.5.6 for Node.js, ECDSA signature malleability occurs because BER-encoded signatures are allowed.

Describe the solution you'd like

Bump to >= 6.5.7

[elgreg]

Based on the fact that this PR from one actual dependency with this issue hasn't been merged since 2021, browserify might be dead browserify/createECDH#20

The other library with this dependency is https://github.com/browserify/crypto-browserify and doesn't even have an issue filed for it. Maybe this ticket should be to move off of browserify.