docs: add docs for `starknet-accounts` #617

Job	Run time
Build C++ integration example	1m 12s
Build starknet-curve features	18s
Build starknet-crypto features	33s
Build starknet-core features	1m 7s
Build starknet-providers features	1m 14s
Build starknet-signers features	54s
Build starknet-accounts features	55s
Build starknet-contract features	51s
Build starknet-macros features	34s
Build starknet features	1m 48s
	9m 26s

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