github action to autogenerate types after chain upgrades

[rjonczy]

Create a Github Action, which will generate new types after upgrades of chains, like describe here:

composable-ibc/utils/subxt/codegen/README.md

Line 18 in 698146a

- composable (mainnet): `cargo run -p codegen --bin codegen -- --path ./utils/subxt/generated/src/composable --relay-url wss://composable-unrpc-lb.composablenodes.tech/relay --para-url wss://composable-unrpc-lb.composablenodes.tech`

Requirements

• initially Action can be triggered manually on demand
• action should create new branch (branch out from main/master)
• auto generate types
• open PR to main/master