Add `isguaranteed` method for `Number` #267

Job	Run time
Documentation	1m 29s
Julia 1.9 - ubuntu-latest - x64 - push	2m 8s
Julia 1.9 - ubuntu-latest - x86 - push	2m 41s
Julia 1.9 - macOS-latest - x64 - push	2m 52s
Julia 1.9 - windows-latest - x64 - push	3m 31s
Julia 1.9 - windows-latest - x86 - push	3m 26s
Julia 1 - ubuntu-latest - x64 - push	2m 1s
Julia 1 - ubuntu-latest - x86 - push	2m 31s
Julia 1 - macOS-latest - x64 - push	2m 8s
Julia 1 - windows-latest - x64 - push	2m 46s
Julia 1 - windows-latest - x86 - push	3m 8s
Julia nightly - ubuntu-latest - x64 - push	2m 44s
Julia nightly - ubuntu-latest - x86 - push	4m 14s
Julia nightly - macOS-latest - x64 - push	3m 3s
Julia nightly - windows-latest - x64 - push	4m 1s
Julia nightly - windows-latest - x86 - push	3m 36s
	46m 19s

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