Improve 'fromString' haddocks #50

Job	Run time
arm (arm32v7)	9m 22s
arm (arm64v8)	8m 51s
build (ubuntu-latest, 8.6, 3.8.1.0)	38m 31s
emulated (s390x)	21m 42s
darwin_arm (self-hosted, macOS, ARM64, 8.10.7)	28m 32s
build (ubuntu-latest, 8.8, 3.8.1.0)	10m 2s
freebsd (self-hosted, FreeBSD, X64, 9.4.8)	6m 6s
darwin_arm (self-hosted, macOS, ARM64, 9.2.8)	20m 20s
emulated (ppc64le)	19m 14s
freebsd (self-hosted, FreeBSD, X64, 9.6.4)	6m 2s
darwin_arm (self-hosted, macOS, ARM64, 9.4.7)	23m 27s
build (ubuntu-latest, 8.10, 3.8.1.0)	11m 17s
i386	9m 53s
build (ubuntu-latest, 9.0, 3.8.1.0)	11m 12s
build (ubuntu-latest, 9.2, 3.8.1.0)	1h 17m 38s
build (ubuntu-latest, 9.4, 3.8.1.0)	9m 56s
build (ubuntu-latest, 9.6, 3.8.1.0)	10m 4s
build (ubuntu-latest, 9.8, 3.8.1.0)	8m 7s
build (macOS-12, 9.4, 3.8.1.0)	1h 50m 13s
build (macOS-12, 9.6, 3.8.1.0)	31m 23s
build (windows-latest, 9.4, 3.8.1.0)	50m 15s
build (windows-latest, 9.6, 3.8.1.0)	49m 32s
	9h 31m 39s

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