chore: add is dynamic fee #867

Job	Run time
cfg-check	50s
doctest	53s
clippy	54s
docs	1m 7s
feature-checks	3m 53s
feature-powerset	5m 3s
fmt	12s
no-std	40s
wasm-unknown	52s
wasm-wasi	45s
test stable --no-default-features	1m 10s
test stable	1m 1s
test stable --all-features	1m 13s
test nightly --no-default-features	1m 33s
test nightly	1m 32s
test nightly --all-features	1m 38s
test 1.81 --no-default-features	42s
test 1.81	42s
	24m 40s

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