Moves images to improved documentation structure

Moves various image files demonstrating libomath’s usage and featuring artwork from showcases to the improved `docs/images` structure to reorganize the project's documentation in a logical and maintainable fashion.

This change ensures consistency and simplifies updating documentation assets.

docs/styles/center.css

@@ -0,0 +1,4 @@
+/* docs/css/custom.css */
+.center-text {
+    text-align: center;
+}