chore: add monad testnet #488

Job	Run time
docs	33s
fmt	11s
clippy	28s
feature-checks	1m 0s
miri --no-default-features	44s
test stable --no-default-features	21s
miri	46s
wasm	25s
test stable	21s
miri --all-features	1m 11s
test stable --all-features	36s
test beta --no-default-features	19s
test beta	19s
test beta --all-features	31s
test nightly --no-default-features	19s
test nightly	20s
test nightly --all-features	31s
test 1.81 --no-default-features	21s
test 1.81	19s
deny / cargo deny check	15s
	9m 50s

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