Credentials: decode simple CredentialType values

[mDuo13]

This applies to CredentialCreate, CredentialAccept, and CredentialDelete transaction views, as well as anywhere else Credential details are displayed (currently I think that's all).

Similar to how the explorer decodes other hex values like accounts' Domain value or extended currency codes, I expect the CredentialType field to be decoded into human-readable text, at least if it decodes into reasonable plain text using ASCII. (Or UTF-8, although that has a lot more edge cases to account for.) Obviously you would want to exclude or escape special characters so that you don't end up with cross-site scripting, or right-to-left text, or other glitchiness, similar to how you do with Domains, Memos, and other examples.

I would expect this to display the CredentialType as test_cred1 for example. (Test transaction on Devnet):

[mvadari]

Credential support hasn't actually been added yet, this is just the default processing.

[ckeshava]

Hello,
DepositPreauth transaction also deals with arrays of credentials. It is helpful to decode those hex-strings as well. Here's an exanple: https://github.com/XRPLF/XRPL-Standards/tree/master/XLS-0070d-credentials#124-depositpreauth