feat: add support for CAP-33

[overcat]

No description provided.

[codecov]

Codecov Report

Merging #372 into dev-protocol-14 will decrease coverage by 0.00%.
The diff coverage is 98.51%.

@@                 Coverage Diff                 @@
##           dev-protocol-14     #372      +/-   ##
===================================================
- Coverage            98.98%   98.98%   -0.01%     
===================================================
  Files                  121      125       +4     
  Lines                 7117     7501     +384     
===================================================
+ Hits                  7045     7425     +380     
- Misses                  72       76       +4     

Flag	Coverage Δ
#unittests	98.98% <98.51%> (-0.01%)	⬇️

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Impacted Files	Coverage Δ
stellar_sdk/signer_key.py	91.42% <91.42%> (ø)
stellar_sdk/operation/revoke_sponsorship.py	98.35% <98.35%> (ø)
stellar_sdk/__init__.py	100.00% <100.00%> (ø)
stellar_sdk/operation/__init__.py	100.00% <100.00%> (ø)
..._sdk/operation/begin_sponsoring_future_reserves.py	100.00% <100.00%> (ø)
...ar_sdk/operation/end_sponsoring_future_reserves.py	100.00% <100.00%> (ø)
stellar_sdk/sep/txrep.py	99.44% <100.00%> (ø)
stellar_sdk/signer.py	100.00% <100.00%> (+2.70%)	⬆️
stellar_sdk/transaction_builder.py	100.00% <100.00%> (ø)
tests/test_operation.py	100.00% <100.00%> (ø)
... and 6 more