feat(examples): add p/demo/seqid #2501

Job	Run time
build (1.20.x, GOARCH=amd64 GOOS=linux, gno)	22s
build (1.20.x, GOARCH=wasm GOOS=js, gno)	26s
test (1.20.x, _test.cmd)	1m 4s
build (1.21.x, GOARCH=amd64 GOOS=linux, gno)	27s
test (1.20.x, _test.pkg)	50s
build (1.21.x, GOARCH=wasm GOOS=js, gno)	22s
test (1.20.x, _test.gnolang.native)	42s
test (1.20.x, _test.gnolang.stdlibs)	56s
test (1.20.x, _test.gnolang.realm)	40s
test (1.20.x, _test.gnolang.pkg0)	1m 42s
test (1.20.x, _test.gnolang.pkg1)	6m 27s
test (1.20.x, _test.gnolang.pkg2)	4m 25s
test (1.20.x, _test.gnolang.other)	35s
test (1.21.x, _test.cmd)	1m 14s
test (1.21.x, _test.pkg)	49s
test (1.21.x, _test.gnolang.native)	32s
test (1.21.x, _test.gnolang.stdlibs)	59s
test (1.21.x, _test.gnolang.realm)	35s
test (1.21.x, _test.gnolang.pkg0)	1m 35s
test (1.21.x, _test.gnolang.pkg1)	6m 8s
test (1.21.x, _test.gnolang.pkg2)	4m 2s
test (1.21.x, _test.gnolang.other)	29s
upload-coverage	20s
	35m 41s

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