bindings: Apple compliant framework distribution

[lvaccaro]

• creating swift bindings
• creating a wrapper project with xcodegen, instead maintain a full .xcproject
• archiving both platforms
• assembling the final xcframework

[LeoComandini]

just-swift gh ci job failed with

      Running `target/debug/lwk_cli generate --library ./target/aarch64-apple-ios/release/liblwk.a --language swift --out-dir ./target/swift`
null
xcodegen generate --spec lwk_bindings/swift/project.yml
sh: xcodegen: command not found
error: Recipe `swift` failed on line 128 with exit code 12

[LeoComandini]

with swift ci fixed lgtm

[LeoComandini]

is

        - run: brew install xcodegen
        - run: just swift

enough?
@lvaccaro

[lvaccaro]

right, it only needs xcodegen as in the Blockstream/lwk-swift#12