Update SEP-01 & improvements

• update SEP-01 currency fields: add contract field
• improve streams in the request builders. see: #90
• update the request builder to maintain the original path and query. see: #89

Update SEP-06

• update SEP-09 fields (see #86)
• update SEP-06 to reflect current SEP-06 doc version. See also: SDK doc. Resolves #87

SEP-38 Support

• add sep-38 support see doc

Sep-009 update

update and extend SEP-009 kyc fields

Soroban & SEP-006 Improvements

• extend soroban send transaction response (see #84)
• improve sep-006 support (see #83)

Support Soroban 20.0.2

• add support for soroban 20.0.2
• this release contains breaking changes, see also #81

Improvements and fixes

• improve handling of horizon responses with status code 429 see issue #78
• fix soroban rpc response for simulate transaction request
• improve a soroban testcase

improve sep-24 support

allow null amounts in sep24 transaction response

SEP-30 Support

• Add support for SEP-30. See example
• Rename expirationLedgerSeq from soroban rpc response

Update for stable P20

• see #75