Language Server

Add language server implementation with support for:

• diagnostics
• go to definition
• list references
• highlight
• hover
• list document symbols
• auto-complete suggestions

Syntax Highlighting

Add syntax highlighting using tree sitter:

• add tree sitter grammar,
• add highlighting queries,
• add docs for setting up highlighting in neovim.

Additionally, this release changes the Position (used by errors) to be measured int UTF-16 offset instead of UTF-8 offset.

Improved nulls

This release improves working with nulls. Changes:

• bool function now behaves as "is truthy" instead of parsing string to bool
• added is_null function, which makes it possible to differentiate between false and null values
• added keyword null which constructs a null value

Initial release

This is the initial release of the aoc interpreter. Intepreter has not been tested thoroughly though, so there might be some bugs.