Update sheetruby to 0.2.0 README

Author: udzura

README.md

@@ -1,2 +1,118 @@
 # sheetruby
-mruby VM in your spreadsheet
+
+Run Ruby code in Google Sheets using [mruby/edge](https://github.com/mrubyedge/mrubyedge)
+
+## What is sheetruby?
+
+sheetruby embeds the [mruby/edge](https://github.com/mrubyedge/mrubyedge) VM into Google Apps Script, allowing you to execute Ruby code directly in your spreadsheets. It compiles to WebAssembly and runs entirely within Google Sheets' Apps Script environment.
+
+## How to Use
+
+1. Open your Google Spreadsheet
+2. Go to **Extensions** → **Apps Script**
+3. Copy the contents of `combined.js` and paste it into the script editor
+4. Save the script
+5. Return to your spreadsheet - the `EVAL_RUBY_SCRIPT()` function is now available!
+
+## `EVAL_RUBY_SCRIPT()` Function Specification
+
+```javascript
+EVAL_RUBY_SCRIPT(ruby_code, [arg1], [arg2], [arg3])
+```
+
+### Parameters
+
+- **First argument (required)**: Ruby script code
+  - Can be a string literal or reference to a cell
+- **Arguments 2-4 (optional)**: Data to pass to the Ruby script
+  - Can reference cells or ranges
+  - Accessible in Ruby as global variables `$arg1`, `$arg2`, `$arg3`
+  - Currently supports up to 3 arguments
+
+### Type Handling
+
+- **Single cell**: Type is automatically inferred (number, string, boolean)
+- **Multiple cells**: Passed as a 2D array (Array of Arrays)
+- **Return value**: Type is automatically inferred from Ruby result via JSON serialization
+
+### Examples
+
+**Basic calculation:**
+```ruby
+=EVAL_RUBY_SCRIPT("1 + 2")
+# => 3
+```
+
+**Using cell references:**
+```ruby
+=EVAL_RUBY_SCRIPT("$arg1 * 2", A1)
+# If A1 = 21, returns 42
+```
+
+**Array processing:**
+```ruby
+=EVAL_RUBY_SCRIPT("$arg1.map { |x| x * $arg2 }", A1:A3, B1)
+# If A1:A3 = [[1], [2], [3]] and B1 = 10
+# Returns [10, 20, 30]
+```
+
+**Multiple arguments:**
+```ruby
+=EVAL_RUBY_SCRIPT("$arg1 + $arg2 + $arg3", A1, B1, C1)
+# Sum of three cells
+```
+
+**String manipulation:**
+```ruby
+=EVAL_RUBY_SCRIPT("$arg1.upcase", A1)
+# If A1 = "hello", returns "HELLO"
+```
+
+**Math functions (with mrubyedge-math):**
+```ruby
+=EVAL_RUBY_SCRIPT("Math.sqrt($arg1)", 16)
+# => 4.0
+```
+
+## Building from Source
+
+### Prerequisites
+
+1. Install [Emscripten SDK](https://emscripten.org/docs/getting_started/downloads.html)
+   ```bash
+   git clone https://github.com/emscripten-core/emsdk.git
+   cd emsdk
+   ./emsdk install latest
+   ./emsdk activate latest
+   source ./emsdk_env.sh
+   ```
+
+2. Install Rust with the `wasm32-unknown-emscripten` target:
+   ```bash
+   rustup target add wasm32-unknown-emscripten
+   ```
+
+3. Set the `BINDGEN_EXTRA_CLANG_ARGS` environment variable:
+   ```bash
+   export BINDGEN_EXTRA_CLANG_ARGS="--sysroot=$EMSDK/upstream/emscripten/cache/sysroot"
+   ```
+
+### Build
+
+```bash
+make build
+```
+
+This will generate `combined.js` in the project root.
+
+## Contributing
+
+Bug reports and contributions are welcome! Please feel free to:
+
+- Report issues on [GitHub Issues](https://github.com/mrubyedge/sheetruby/issues)
+- Submit pull requests
+- Share your use cases and feedback
+
+## License
+
+See [LICENSE](LICENSE) file for details.