add test inputs and README for llappearanceutility

Author: rohvani

indra/llappearanceutility/README.md

@@ -0,0 +1,33 @@
+# llappearanceutility
+
+This directory contains the appearance utility employed by the bake service to process avatar textures and handle various other appearance-related functions. Please note that this utility is currently configured to build only on Linux systems.
+
+## Prerequisites
+
+Ensure the following prerequisites are met before building and testing the utility:
+
+- **X11 Display**: Ensure an X11 display is available, either virtual or physical, with the `DISPLAY` environment variable set appropriately (e.g., `DISPLAY=:1`).
+- **Linux Build Environment**: Confirm that the Second Life Viewer can be built on your Linux system.
+
+## Testing
+
+Given the constraints with GitHub runners, we instead utilize Behavior-Driven Development (BDD) tests to evaluate the `llappearanceutility` through the bake service. For local development, test inputs and their expected outputs are provided below.
+
+### Test Commands
+
+1. **Baking Textures**:
+    ```sh
+    appearance-utility-bin --agent-id de494a4f-f01a-47a4-98cf-c94ef9ecca38 --texture /viewer/indra/llappearanceutility/tests/texture.llsd > /viewer/indra/llappearanceutility/tests/texture.llsd.output
+    ```
+
+2. **Generating Bake Parameters**:
+    ```sh
+    appearance-utility-bin --agent-id de494a4f-f01a-47a4-98cf-c94ef9ecca38 --params /viewer/indra/llappearanceutility/tests/params.xml > /viewer/indra/llappearanceutility/tests/params.xml.output
+    ```
+
+3. **Calculating Joint Offsets**:
+    ```sh
+    appearance-utility-bin --agent-id de494a4f-f01a-47a4-98cf-c94ef9ecca38 --joint-offsets /viewer/indra/llappearanceutility/tests/joint-offsets.xml > /viewer/indra/llappearanceutility/tests/joint-offsets.xml.output
+    ```
+
+These commands will execute the utility with specific test inputs and direct the output to corresponding files for validation.