feat(sdk): implement depositETH

fix(contracts): remove broken link in README

Implements the depositETH function for the upcoming Optimism JS SDK.
Very basic functionality, only allows users to deposit to their own
accounts. We can consider adding the ability to deposit to other
accounts as part of a future PR.

go/proxyd: Add debug cache status header to HTTP responses

feat(sdk): implement resendMessage

feat(sdk): implement sendMessage

feat: implement getMessageStatus

Version Packages

Develop -> Master PR

Update README.md

l2geth: fix nonce issue

chore(deps): bump node-fetch from 2.6.1 to 2.6.7

proxyd: Allow cached RPC keys to be evicted

go/proxyd: Add additional itests for cache, changeset

Bumps [node-fetch](https://github.com/node-fetch/node-fetch) from 2.6.1 to 2.6.7.
- [Release notes](https://github.com/node-fetch/node-fetch/releases)
- [Commits](https://github.com/node-fetch/node-fetch/compare/v2.6.1...v2.6.7)

---
updated-dependencies:
- dependency-name: node-fetch
  dependency-type: direct:production
...
Signed-off-by: dependabot[bot] <support@github.com>

go/batch-submitter: Add releases for go BSS

feat(sdk): implement L2 message gas estimation

maintenance: clean up typings in core utils

maintenance: improved docstrings for BCFG

l2geth: better error message for proxying user txs

This commit adds a better error message when there
is an error for proxying user requests to the sequencer.
This allows the change to be relatively backwards compatible
as a good error message is returned when the sequencer url
is not configured.