Add N8N integration docs

[TC-MO]

We've got a new integration for N8N. We need to add this to documentation. First draft will be prepared and from that we need to:

Go over first draft. Move it in .md to our documentation. Adjust the style based on Apify style guide.

AC:

• Review first draft for Gumloop docs
• Remake docs into .md & add them into our docs
• Adjust docs based on Apify style guide
• Double check instructions & images