Fix: Accept numeric version field in AnkiConnect API requests

[mallomar]

Fixes KOReader Anki plugin compatibility by accepting numeric version fields in API requests.

Problem

KOReader sends {"version":6,"action":"requestPermission"} with version as a number (per the official AnkiConnect API spec), but AnkiConnect Android was rejecting this with a MalformedJsonException at column 14 (immediately after the numeric 6).

Solution

1. Made the JSON parser lenient to accept both numeric and string version fields
2. Updated get_version() to explicitly handle both number and string types for the version field

Testing

• The official AnkiConnect API spec uses version as a number
• This maintains backward compatibility with clients that send version as a string (like Yomitan)
• Fixes #[89]

Related issue: #89