Unintuitive naming on signTransaction() and signCotaNFTTx().

[jordanmack]

In @joyid/ckb, the functions signTransaction() and signCotaNFTTx() have slightly different functionality than is indicated.

signTransaction(): Creates a transaction to send CKB and signs it without broadcasting.
signCotaNFTTx(): Creates a transaction to send a CoTA NFT and signs it without broadcasting.

At a glance, more fitting function names would be something like sendCkbTx() and sendCotaNftTx().

[duanyytop]

We hope Dapps will send the signed transaction by themselves, not the JoyID app and this is more general.

So I think the prefix sign makes more sense and maybe signTransferTx is better than signTransaction.