Docs: Transaction Page improvements

This issue refers to the following page: https://0xmiden.github.io/miden-docs/imported/miden-base/src/transaction.html#flow

There are two things that can be improved on the Notes page documentation. Here's the list:

### 1. Network Transaction Status

**Issue:** Documentation states network transactions are not yet implemented
- **Action needed:** Update to reflect that network transactions are now implemented

### 2. Transaction Flow explanation

**Issue:** The Flow explanation feels a bit arbitrary with not much explanation around it.
- **Suggested improvement:** Add a link to the .masm files of the miden-base repository, where devs can directly see the logic of the transaction kernel. This helps in understanding how the transaction kernel and flow works under the hood