build(flake.nix/inputs): Add `devenv`

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Below you will find a summary of the cachix status of each package, for each supported platform.

package	x86_64-linux	x86_64-darwin	aarch64-darwin
avalanche-cli	✅ cached	✅ cached	✅ cached
blst	✅ cached	✅ cached	✅ cached
bnb-beacon-node	✅ cached	✅ cached	✅ cached
cardano	✅ cached	✅ cached	🚫 not supported
cdt	✅ cached	🚫 not supported	🚫 not supported
circ	✅ cached	✅ cached	✅ cached
circom	✅ cached	✅ cached	✅ cached
circom_runtime	✅ cached	✅ cached	✅ cached
corepack-shims	✅ cached	✅ cached	✅ cached
cosmos-theta-testnet	✅ cached	✅ cached	✅ cached
cryptography36	✅ cached	🚫 not supported	🚫 not supported
emscripten	✅ cached	✅ cached	✅ cached
eos-vm	✅ cached	🚫 not supported	🚫 not supported
ffiasm	✅ cached	✅ cached	🚫 not supported
ffiasm-src	✅ cached	✅ cached	🚫 not supported
gaiad	✅ cached	✅ cached	✅ cached
go-opera	✅ cached	✅ cached	✅ cached
graphql	✅ cached	✅ cached	🚫 not supported
leap	✅ cached	🚫 not supported	🚫 not supported
pistache	✅ cached	🚫 not supported	🚫 not supported
polkadot	✅ cached	✅ cached	✅ cached
polkadot-fast	✅ cached	✅ cached	✅ cached
py-ecc	✅ cached	🚫 not supported	🚫 not supported
rapidsnark	✅ cached	✅ cached	🚫 not supported
rapidsnark-server	✅ cached	🚫 not supported	🚫 not supported
wasmd	✅ cached	🚫 not supported	🚫 not supported
zqfield-bn254	✅ cached	✅ cached	🚫 not supported