Add Golang client for Stellar RPC #80

Job	Run time
Build (ubuntu-latest, x86_64-unknown-linux-gnu, amd64)	3m 18s
Unit tests (ubuntu-20.04)	4m 21s
Build (ubuntu-latest, aarch64-unknown-linux-gnu, arm64)	3m 34s
Unit tests (ubuntu-22.04)	3m 56s
Build (macos-latest, x86_64-apple-darwin, amd64)	6m 59s
Integration tests (ubuntu-20.04, 21)	7m 43s
Build (macos-latest, aarch64-apple-darwin, arm64)	7m 10s
Integration tests (ubuntu-20.04, 22)	8m 7s
Build (windows-latest, x86_64-pc-windows-gnu, amd64)	12m 9s
Integration tests (ubuntu-22.04, 21)	7m 34s
Integration tests (ubuntu-22.04, 22)	8m 7s
	1h 12m 58s

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