Add development README

Author: davidisaaclee

README.md

@@ -0,0 +1,22 @@
+# vsynth
+
+A modular video synthesizer for the web browser.
+
+## Development
+
+```bash
+# Clone repository.
+git clone https://github.com/davidisaaclee/vsynth
+cd vsynth
+
+# Install dependencies.
+yarn
+
+# Build GLSL assets; required for first run.
+# You'll need to run this again if you change any .glsl files.
+yarn run build:glslify
+
+# Start a development server on `localhost:3000`.
+yarn start
+```
+