Release 0.4.0

[density215]

Release 2025-01-29.

Breaking changes

• Filter maps no longer have a define and an apply block. let bindings
  should be used instead. For example:

# Roto 0.3
filter-map foo() {
    define {
        x = 4;
    }
    apply {
        accept x;
    }
}

# Roto 0.4
filter-map foo() {
    let x = 4;
    accept x;
}

New

• Variables can now be created in more places with let bindings. let
  bindings replace the define/apply mechanism and are much more general
  because they can be used in any block. For example, inside functions or
  if-else blocks. The binding is scoped until the end of the block it is
  defined in. It is not allowed to declare multiple variables with the same
  name within a single block.
• The String type was added to represent pieces of text. String literals
  are enclosed in double quotes (").
• It is now possible to declare constants in the runtime for a Roto script.
• Similarly, it is now possible to add "context" to Roto scripts. The variables
  in the context behave like constants, but they can differ between different
  calls to a script. In other words, constants are defined when the script is
  compiled, context is defined when the script is run.

Bug fixes

• 64-bit numbers (i.e. i64 and u64) were not type checked and compiled
  properly. They are now fixed.