build: add Dockerfile to generate and server libghostty c docs

src/build/docker/lib-c-docs/Dockerfile

@@ -0,0 +1,21 @@
+#--------------------------------------------------------------------
+# Generate documentation with Doxygen
+#--------------------------------------------------------------------
+FROM ubuntu:24.04 AS builder
+RUN apt-get update && apt-get install -y \
+    doxygen \
+    graphviz \
+    && rm -rf /var/lib/apt/lists/*
+WORKDIR /ghostty
+COPY include/ ./include/
+COPY Doxyfile ./
+RUN mkdir -p zig-out/share/ghostty/doc/libghostty
+RUN doxygen
+
+#--------------------------------------------------------------------
+# Host the static HTML
+#--------------------------------------------------------------------
+FROM nginx:alpine AS runtime
+COPY --from=builder /ghostty/zig-out/share/ghostty/doc/libghostty /usr/share/nginx/html
+EXPOSE 80
+CMD ["nginx", "-g", "daemon off;"]