chore: add doxygen config, gitignore entries, and pgs API stubs for documentation build

docs/index.md

@@ -0,0 +1,21 @@
+# Pretty Good Server API 
+
+# Reference
+
+::: pgscript
+::: pgs
+
+For project page visit [molodetz.nl](https://molodetz.nl).
+
+## Commands
+
+* `build build` - Builds application and formats source.
+* `build run` - Builds application and runs it.
+
+## Project layout
+
+    pgs.c # Main application.
+    py.h  # Python plugin handler.
+    pgscript.py # Script to be defined by user.
+    pgs.py # Dummy file representing the pgs api.
+    pgs_api.h # Actual C application.