docs: add docs for `starknet-macros` #1389

Job	Run time
no-std build	46s
Unix tests (ubuntu-latest, stable)	1m 58s
WASM tests	3m 49s
Unix tests (ubuntu-latest, nightly)	1m 40s
Windows tests (stable, x86_64-pc-windows-gnu)	5m 35s
Unix tests (macos-12, stable)	3m 6s
Windows tests (stable, x86_64-pc-windows-msvc)	4m 53s
Unix tests (macos-12, nightly)	2m 28s
Windows tests (nightly, x86_64-pc-windows-gnu)	4m 43s
Windows tests (nightly, x86_64-pc-windows-msvc)	5m 16s
	34m 14s

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