Update index.html.erb.md
Update labels.html.erb.md
Update structure.html.erb.md
Update instructions.html.erb.md
Update error-prevention.html.erb.md
Update error-messages.html.erb.md
Create multi-step
Update in-disguise.html.erb.md
Fixed routing
Rename to custom controls, order in navigation
Update labels.html.erb.md
Validating and User Interaction
Rename validating-input.html -> validation.html
Clean up labels

Remove notes where the text is not a not but actually quite essential, also updated typography.
Rename structure to grouping

Remove now unneccessary techniques/success criteria
Make comments in code examples readable
Typography
Wording
Wording
Expand on keywords provided by @Nitedog