Make Tp-Note (also) a library

[getreu]

Use case

Expose Tp-Note's core functionality for simple embedding in text editors or text editor plugins.

Todo

Requires effortful refactoring, e.g.:

• Refactor lazy static configuration variables into some configuration object on the heap.
• Use the builder pattern for configuration objects.
• Start by exposing the note module in note.rs.

[getreu]

A first alpha version 0.7.0 is out: tpnote-lib - crates.io: Rust Package Registry The API might still slightly change until v1.0.0, consider it as a preview. Feedback is welcome.