Implement loading HTML from http.FileSystem #1614

Job	Run time
lint	18s
ubuntu-latest @ Go 1.21	37s
ubuntu-latest @ Go 1.21 -tags nomsgpack	35s
ubuntu-latest @ Go 1.21 -tags "sonic avx"	59s
ubuntu-latest @ Go 1.21 -tags go_json	41s
ubuntu-latest @ Go 1.21 -race	17s
ubuntu-latest @ Go 1.22	38s
ubuntu-latest @ Go 1.22 -tags nomsgpack	31s
ubuntu-latest @ Go 1.22 -tags "sonic avx"	51s
ubuntu-latest @ Go 1.22 -tags go_json	40s
ubuntu-latest @ Go 1.22 -race	16s
macos-latest @ Go 1.21	33s
macos-latest @ Go 1.21 -tags nomsgpack	35s
macos-latest @ Go 1.21 -tags "sonic avx"	32s
macos-latest @ Go 1.21 -tags go_json	43s
macos-latest @ Go 1.21 -race	19s
macos-latest @ Go 1.22	36s
macos-latest @ Go 1.22 -tags nomsgpack	32s
macos-latest @ Go 1.22 -tags "sonic avx"	34s
macos-latest @ Go 1.22 -tags go_json	48s
macos-latest @ Go 1.22 -race	19s
	11m 54s

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