The module was barely used, and its presence confusing, since
WebCrypto or asmcrypto are often directly used and usable instead.
Also, use AES_CBC instead of AES_ECB for single-block encryption,
so that we can drop support for the latter in the asmcrypto lib.
Mocha v10 requires the lib to be esm compliant.
ESM mandates the use of file extensions in imports, so to minimize the
changes (for now), we rely on the flag `experimental-specifier-resolution=node`
and on `ts-node` (needed only for Node 20).
Breaking changes:
downstream bundlers might be affected by the package.json changes depending on
how they load the library.
NB: legacy package.json entrypoints are still available.
