Add zksync flag to contract deployment

[valle-xyz]

Adds an optional flag to inform about an env variable needed to deploy ZKsync chains.

[github-actions]

Branch preview

✅ Deployed successfully in branch deployment:

https://addzksyncflagtocontractdeployment--docs.review.5afe.dev

[github-actions]

Overall readability score: 42.49 (🟢 +11.52)

File	Readability
safe-contracts-deployment.mdx	52.78 (🟢 +0)

View detailed metrics

🟢 - Shows an increase in readability
🔴 - Shows a decrease in readability

File	Readability	FRE	GF	ARI	CLI	DCRS
safe-contracts-deployment.mdx	52.78	40.14	8.24	14.5	14.9	7.57
	🟢 +0	🟢 +0	🟢 +0	🟢 +0	🟢 +0	🟢 +0

Averages:

	Readability	FRE	GF	ARI	CLI	DCRS
Average	42.49	37.14	12.06	15.82	14.37	8.22
	🟢 +11.52	🟢 +10.76	🟢 +1.44	🟢 +2.25	🟢 +1.57	🟢 +0.56

View metric targets

Metric	Range	Ideal score
Flesch Reading Ease	100 (very easy read) to 0 (extremely difficult read)	60
Gunning Fog	6 (very easy read) to 17 (extremely difficult read)	8 or less
Auto. Read. Index	6 (very easy read) to 14 (extremely difficult read)	8 or less
Coleman Liau Index	6 (very easy read) to 17 (extremely difficult read)	8 or less
Dale-Chall Readability	4.9 (very easy read) to 9.9 (extremely difficult read)	6.9 or less

[valle-xyz]

Closed in favor of #640