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

Protocol 20 Support

• update horizon responses for p20
• remove soroban experimental flag

soroban prev. 11 support (multisig)

• add multisig to soroban prev. 11 support

support soroban prev 11

add support for soroban prev 11

anchor handling improvements

• anchor handling improvements - sep001, sep009, sep0010, sep0012, sep024
• preparations for web support