Unclear how to transfer ETH from L1 to L2 using bridge

[platocrat]

Description
The docs don't make it clear how a user should transfer ETH from L1 to L2 using bridge contracts.
Here are some paraphrased issues surfaced by @funfair-tech and discussion with @snario:

• Not clear whether we should use transfer or the deposit method to get ETH to L2. When do you use which method?
• We should have integration tests around sending WETH from one L2 address to another

Motivation

• From our docs, it should be clear when to use deposit, transfer, or transferFrom on L1 and L2.
• Each method should ideally have its own outlined "flow" for users and developers to understand the higher-level process of each.

Estimated effort and complexity

• Effort: 1-2
• Complexity: 0

Tags to related packages

• contracts