Introduce `HTTPExt` package extension #315

Job	Run time
Julia 1 - macOS-13 x64	4m 1s
Julia 1 - macOS-latest aarch64	3m 47s
Julia 1 - ubuntu-latest x64	3m 36s
Julia 1 - windows-latest x64	4m 29s
Julia lts - macOS-13 x64	2m 45s
Julia lts - macOS-latest aarch64	1m 55s
Julia lts - ubuntu-latest x64	2m 8s
Julia lts - windows-latest x64	3m 31s
Julia 1.6 - macOS-13 x64	3m 52s
Julia 1.6 - ubuntu-latest x64	3m 32s
Julia 1.6 - windows-latest x64	10m 43s
Julia 1 - ubuntu-latest x86	4m 10s
Julia nightly - ubuntu-latest x64	5m 12s
	53m 41s

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