Initial commit of a toy analogue audio generator

Key components:
- no_std core so it can be used bare metal on embedded systems
- default implementation for RPi 2350, with midi input and I2s output using PIO
- Visualiser for the web to play with on a dev system

crates/synth-visualiser/Cargo.toml

@@ -0,0 +1,55 @@
+[package]
+name    = "synth-visualiser"
+version = "0.1.0"
+edition = "2021"
+description = "Browser-based visualiser for the synthesiser (WASM)"
+publish = false
+
+[lib]
+crate-type = ["cdylib", "rlib"]
+
+[features]
+default = ["console-panic"]
+console-panic = ["dep:console_error_panic_hook"]
+
+[dependencies]
+synth-core           = { path = "../synth-core" }
+wasm-bindgen         = { workspace = true }
+wasm-bindgen-futures = { workspace = true }
+js-sys               = { workspace = true }
+serde                = { workspace = true }
+console_error_panic_hook = { workspace = true, optional = true }
+
+[dependencies.web-sys]
+version  = "0.3"
+features = [
+    "Window",
+    "Document",
+    "Element",
+    "HtmlElement",
+    "HtmlCanvasElement",
+    "CanvasRenderingContext2d",
+    "AudioContext",
+    "AudioContextOptions",
+    "AnalyserNode",
+    "GainNode",
+    "OscillatorNode",
+    "OscillatorType",
+    "AudioWorkletNode",
+    "AudioWorkletNodeOptions",
+    "AudioBuffer",
+    "AudioBufferSourceNode",
+    "Event",
+    "EventTarget",
+    "MouseEvent",
+    "PointerEvent",
+    "WheelEvent",
+    "Performance",
+    "Worker",
+    "MessageEvent",
+    "AudioNode",
+    "AudioDestinationNode",
+]
+
+[dev-dependencies]
+wasm-bindgen-test = "0.3"