Add basic support for AnkiConnect (WIP)

[MarkoSagadin]

This is a prototype implementation.

In the current state the md2anki will:

• Send processed cards to the Anki via 'addNote' API
• Send images to the Anki via 'storeMediaFile' API
• Display basic info when that is being done
• Display error messages if any step fails

This feature is far from done:

• deck name and note type are currently hardcoded, they should be provided by the caller for each card/note.
• error handling and validation are missing.
• code style will probably need to be adjusted.

There are several TODO comments that ask questions.

Related: #3

[MarkoSagadin]

I should add that I was testing the AnkiConnect functionality with this example markdown text.

It works as expected, everything is sent over to the Anki.

[Mochitto]

Integration of this PR:

• resolves #6
• resolves #3
• resolves #20

[Mochitto]

Steps needed to implement the feature:

• [x] Update the flow of the app to check for anki-connect; if there is none, throw an error
• [ ] Send a demo card to anki (mvp)
• [ ] Fetch decks and note types from anki (or expose specific note types)
• [ ] Process possible metadata coming from cards and create the data-structure to send all the metadata to anki
• [ ] When processing a card, check if the note type/deck exists else write error to card and dump it to "bad cards", else send it to anki
• [ ] Add support for sending images
• [ ] Isolate the process that creates CSV files as a fall-back for when users do not have AnkiConnect (or prefer files for any reason), signed as "legacy" in the config
• [ ] Add CSV/AnkiConnect option in the config file
• [ ] Add ankiConnect's url to the config (for users that set it up to be a remote connection/something other than the default)
• [ ] Handle edge cases (connection errors, anki connect errors, duplicate cards)