docs: Safe Smart Account docs improvements

[akshay-ap]

Fixes https://github.com/safe-global/developer-experience/issues/243

Changes in PR-

• Improve Overview page for Safe Smart Account

[github-actions]

Branch preview

✅ Deployed successfully in branch deployment:

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

[github-actions]

Overall readability score: 30.81 (🔴 -0.6)

File	Readability
smart-account-overview.mdx	63.99 (🟢 +41.15)

View detailed metrics

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

File	Readability	FRE	GF	ARI	CLI	DCRS
smart-account-overview.mdx	63.99	46.17	9.18	11.6	12.06	6.45
	🟢 +41.15	🟢 +12.63	🟢 +5.17	🟢 +8.6	🟢 +6.45	🟢 +2.68

Averages:

	Readability	FRE	GF	ARI	CLI	DCRS
Average	30.81	26.78	13.65	17.76	15.81	8.96
	🔴 -0.6	🔴 -0.58	🟢 +0.04	🔴 -0.36	🔴 -0.08	🟢 +0.02

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

[germartinez]

I updated the style of the diagrams.
Can we use this version instead?