Add docs for N8N_PROXY_HOPS and mention it in webhook help guide

[Joffcom]

Quick update to document N8N_PROXY_HOPS unless we plan to remove it

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[github-actions]

Overall readability score: 44.18 (🟢 +0)

File	Readability
deployment.md	70.82 (🔴 -0.06)
common-issues.md	86.79 (🔴 -1.26)

View detailed metrics

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

File	Readability	FRE	GF	ARI	CLI	DCRS
deployment.md	70.82	61.12	7.81	8.8	10.76	7.66
	🔴 -0.06	🟢 +0.1	🟢 +0.1	🟢 +0	🔴 -0.06	🔴 -0.05
common-issues.md	86.79	77.13	6.48	6.6	8.04	6.41
	🔴 -1.26	🔴 -0.3	🔴 -0.31	🔴 -0.2	🟢 +0	🔴 -0.12

Averages:

	Readability	FRE	GF	ARI	CLI	DCRS
Average	44.18	35.22	11.44	14.7	14.29	8.46
	🟢 +0	🟢 +0	🟢 +0	🟢 +0	🟢 +0	🟢 +0

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

[imchairmanm]

Just some minor wording / formatting ideas, but looks good 👍