bls

Describe the bug

Export this file in the root index https://github.com/ChainSafe/bls/blob/master/src/errors.ts

Expected behavior

Be able to import those errors from `import {CustomError} from "@chainsafe/bl

#43 and #44 required almost a day of investigation for what was initializing a BigInt by iterative sum, except that the result was not properly zero-initialized and so if the sum didn't reach all the limbs the last limbs stayed uninitialized.

We need tests to ensure that:

• BIG384 (SecretKey)
• ECP (PublicKey)
• ECP2 (Signature / Proof-of-Possession)
  are properly initialized even if the des