(13/17) Creates `XRPPaymentChannelCreate` Protobuf Wrapper Class

[amiecorso]

High Level Overview of Change

This PR implements the class XRPPaymentChannelCreate - a native Swift struct to wrap the PaymentChannelCreate protocol buffer. See also https://xrpl.org/paymentchannelcreate.html

Context of Change

Effort to implement additional XRPL transaction types beyond Payment in the SDK.

Type of Change

• [x] New feature (non-breaking change which adds functionality)
• [x] Tests (You added tests for code that already exists, or your new feature included in this PR)

Before / After

XRPPaymentChannelCreate class and conversion unit tests now exist.

Test Plan

Unit tests added to verify conversion. CI passes.

Future Tasks

[codecov[bot]]

Codecov Report

Merging #282 into master will decrease coverage by 0.06%. The diff coverage is 87.50%.

@@            Coverage Diff             @@
##           master     #282      +/-   ##
==========================================
- Coverage   90.77%   90.71%   -0.07%     
==========================================
  Files          57       58       +1     
  Lines        1258     1282      +24     
==========================================
+ Hits         1142     1163      +21     
- Misses        116      119       +3     

Impacted Files	Coverage Δ
...lCreate+Org_Xrpl_Rpc_V1_PaymentChannelCreate.swift	87.50% <87.50%> (ø)

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