Add editor to items prop in suggestion plugin

[philippkuehn]

With this small breaking change, editor is added to the items prop in the suggestion plugin. This is useful because you can now access the new editor storage when filtering items.

Before:

Suggestion({
  char: '@',
  items: (query) => {
    // filter some items based on query
  },
  // ...
})

After:

Suggestion({
  char: '@',
  items: ({ editor, query }) => {
    // filter some items based on query
  },
  // ...
})