0.1v: basic features

added lexer, parser, Shell, Executor.
added tests for sonyalib
it already works! will be implementing more features soon.

README.md

@@ -0,0 +1,43 @@
+# sonya
+
+A lightweight `just`-like task runner written in Swift.
+
+Define recipes in a `sonyafile` and run them with `sonya <recipe>`.
+
+## sonyafile syntax
+
+```
+CC = clang
+FLAGS = -O2
+
+build:
+    $(CC) $(FLAGS) main.c -o main
+
+run: build
+    ./main
+
+clean:
+    rm -f main
+```
+
+- Variables are defined as `key = value` and referenced as `$(key)`
+- Recipes can declare dependencies after the colon - they run first
+- Commands are indented with whitespace
+
+## Install
+
+```sh
+swift build -c release
+cp .build/release/sonya /usr/local/bin/sonya
+```
+
+## Usage
+
+```sh
+sonya build    # run a specific recipe
+sonya          # runs "default" recipe
+```
+
+## Roadmap
+
+- Command-line argument passing to recipes (`$1`, `$2`, ...)