This extends exporter.koplugin with support for [Readwise.io](https://readwise.io), a highlight/notes aggregation service.
[Readwise API documentation](https://readwise.io/api_deets)
This additionally improves the highlight exporter's ability to get the correct title and author of a document, by checking actual metadata instead of inferring from filename. It also includes a modification to the plugin's highlight parsing logic to separate the highlight contents in `.text` from the notes in `.note`. This change actually fixes an existing bug in the HTML export template note.tpl, which has been missing notes because of the lack of the `.note` field.
3cf3c97e87