Add worker to the html mode

This adds syntax checking (not validating). Based on HTML5 @aredridel parser
added Gherkin highlighting support
add Gherkin highlighting
make demo more expressive
add tags to the demo
Add auto magic complete (complete while typing)
Fix: skip auto magic completion when pasting

This can some times cause confusing behavior.

A paste is any text insertion of more than one character at a time …
Don't attach/detach autocomplete on change if already attached/detached
Enable auto magic complete only when typing

We only want to auto magically complete when the user is typing text,
not when text is pasted or being removed.
Don't autoInsert with auto magic completer

This caused completions to be inserted without ever being shown, if
they were the only completion for the prefix entered.
Close auto magic complete when prefix is empty

While removing text
Apply editor theme to autocomplete popup
Set default theme for autocomplete popup
replaced tokenizer with highlightrules
added license to files
Use event afterExec instead of change for live autocomplete
use _signal where possible
fix error marker column
Improve autocomplete support for async completers
Improve autocomplete results display and filtering

Autocomplete: Display unique results when it's a snippet

Fix autocomplete popup display

Remove listener for afterExec when enableBasicAutocompletion change

Fix autocomplete detach when no results are ready from the first completer

Remove condition from detach