Make a subset of heraldcore's functionality usable in headless situations

[BaeoMaltinsky]

Possible directions (not mutually exclusive):

• Expose NodeJS bindings (via neon): This is preferable to WebAssembly for a number of reasons. neon is fairly mature and makes heraldcore functionality drivable from Node.
• Expose Python bindings (via PyO3): We know from experience that this is easy, if a bit rough.
• Make heraldcore's public Rust API more ergonomic: This is something that we should do anyway.
• Manually expose C-API: This will be painful to do safely given how complex the data is (we can say this from experience), unless we lean heavily on serializing data structures to cross the FFI boundary.
• Expose C++ and JNI bindings (via rust_swig): I'm not sure how mature or robust rust_swing is, so this may not be the correct approach. jni-rs may be a better solution for JVM languages.
• Expose Lua bindings (via rlua). It's unclear how many people would use this.
• Use socket-based RPC like neovim. This is almost certainly something we want eventually, much easier to do safely than many of the other approaches, and something we have fairly extensive experience with.