update BlockfrostProvider constructor
- check for valid 1st argument - replace wrong blockfrost urls in playground example
- check for valid 1st argument - replace wrong blockfrost urls in playground example
Feature update/script metadata
feat: update/sign tx only witness set
- this prevents 'XMLHttpRequest is not defined' error when the code is executed inside node.js environment
- remove useless utf8 string validation - fix returned type of `toBytes` func - clean up code by reuising `isHexString`
docs: improve contributing