Performance and layout improvements

With this release layout (especially during resizing on macOS) and performance is significantly improved. Moreover, the following features were added:

• Text may be either wrapped (default) or the code view is horizontally scrollable. This is controlled via the LayoutConfiguration passed to the code view.
• First pieces of support for an external language service (such as an LSP server). So far, information lookups are fully supported (e.g., the kind of information produced by an LSP hover request). Semantic tokens are partially implemented — the extra highlighting is missing, see #70.

Finally, there are the obligatory bug fixes.

NB: The location data type changed. This is an (easy to fix) breaking change.