feat: add r/demo/foo20_lp #2416

Job	Run time
build (1.20.x, GOARCH=amd64 GOOS=linux, gno)	47s
build (1.20.x, GOARCH=wasm GOOS=js, gno)	28s
build (1.21.x, GOARCH=amd64 GOOS=linux, gno)	28s
build (1.21.x, GOARCH=wasm GOOS=js, gno)	23s
test (1.20.x, _test.cmd)	1m 7s
test (1.20.x, _test.pkg)	55s
test (1.20.x, _test.gnolang.native)	35s
test (1.20.x, _test.gnolang.stdlibs)	58s
test (1.20.x, _test.gnolang.realm)	40s
test (1.20.x, _test.gnolang.pkg0)	2m 24s
test (1.20.x, _test.gnolang.pkg1)	6m 17s
test (1.20.x, _test.gnolang.pkg2)	7m 8s
test (1.20.x, _test.gnolang.other)	28s
test (1.21.x, _test.cmd)	1m 2s
test (1.21.x, _test.pkg)	1m 15s
test (1.21.x, _test.gnolang.native)	27s
test (1.21.x, _test.gnolang.stdlibs)	1m 25s
test (1.21.x, _test.gnolang.realm)	1m 2s
test (1.21.x, _test.gnolang.pkg0)	1m 31s
test (1.21.x, _test.gnolang.pkg1)	9m 14s
test (1.21.x, _test.gnolang.pkg2)	5m 15s
test (1.21.x, _test.gnolang.other)	31s
upload-coverage	17s
	44m 37s

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