docs: Add N8N_FORMDATA_FILE_SIZE_MAX env var

[ivov]

Ref: n8n-io/n8n#10857

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[github-actions]

Overall readability score: 43.82 (🟢 +0)

File	Readability
endpoints.md	74.77 (🟢 +0.35)

View detailed metrics

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

File	Readability	FRE	GF	ARI	CLI	DCRS
endpoints.md	74.77	61.93	6.06	8.9	10.81	7.34
	🟢 +0.35	🔴 -0.11	🟢 +0.06	🟢 +0.1	🟢 +0.06	🟢 +0.01

Averages:

	Readability	FRE	GF	ARI	CLI	DCRS
Average	43.82	35.23	11.53	14.78	14.3	8.49
	🟢 +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

[freakwriter]

Looks good to me, @ivov !