Initial release: Go Jdenticon library v0.1.0

- Core library with SVG and PNG generation
- CLI tool with generate and batch commands
- Cross-platform path handling for Windows compatibility
- Comprehensive test suite with integration tests

internal/renderer/doc.go

@@ -0,0 +1,58 @@
+/*
+Package renderer is responsible for translating the intermediate representation of an
+identicon (generated by the `engine` package) into a final output format, such
+as SVG or PNG.
+
+This package is internal to the jdenticon library and its API is not guaranteed
+to be stable. Do not use it directly.
+
+# Core Concept: The Renderer Interface
+
+The central component of this package is the `Renderer` interface. It defines a
+contract for any format-specific renderer. The primary method, `Render`, takes a
+list of shapes and colors and writes the output to an `io.Writer`.
+
+This interface-based approach makes the system extensible. To add a new output
+format (e.g., WebP), one would simply need to create a new struct that implements
+the `Renderer` interface.
+
+# Implementations
+
+  - svg.go: Provides `SvgRenderer`, which generates a vector-based SVG image. It
+    builds an XML tree representing the SVG structure and writes it out. This
+    renderer is highly efficient and produces scalable output that maintains
+    visual compatibility with the JavaScript Jdenticon library.
+
+  - png.go: Provides `PngRenderer`, which generates a raster-based PNG image. It
+    utilizes Go's standard `image` and `image/draw` packages to draw the shapes onto
+    a canvas and then encodes the result as a PNG.
+
+  - fast_png.go: Provides `FastPngRenderer`, an optimized PNG implementation that
+    uses more efficient drawing algorithms for better performance in high-throughput
+    scenarios.
+
+# Rendering Pipeline
+
+The rendering process follows this flow:
+
+ 1. The engine package generates `RenderedElement` structures containing shape
+    geometries and color information.
+
+ 2. A renderer implementation receives this intermediate representation along with
+    size and configuration parameters.
+
+ 3. The renderer translates the abstract shapes into format-specific commands
+    (SVG paths, PNG pixel operations, etc.).
+
+ 4. The final output is written to the provided `io.Writer`, allowing for
+    flexible destination handling (files, HTTP responses, etc.).
+
+# Performance Considerations
+
+The renderers are designed for efficiency:
+- SVG rendering uses a `strings.Builder` for efficient, low-allocation string construction
+- PNG rendering includes both standard and fast implementations
+- All renderers support concurrent use across multiple goroutines
+- Memory allocations are minimized through object reuse where possible
+*/
+package renderer