Add utilities and documentation

Add portable filesize and logging C libraries and documentation for development.

.gitignore

@@ -11,7 +11,6 @@
 !build.sh
 !CHANGELOG
 !configure.ac
-!extension_api.json
 !LICENSE
 !Makefile.am
 !README
@@ -34,12 +33,21 @@
 !/bld/src/d/dub.sdl
 !/bld/src/d/dub.selections.json
 
-# /docs
-!/docs/
-/docs/*
+# /doc
+!/doc/
+/doc/*
 
-!/docs/1.1_ACKNOWLEDGMENTS
-!/docs/1.2_PRIVACY
+!/doc/1.1_ACKNOWLEDGMENTS
+!/doc/1.2_PRIVACY
+
+# /doc/2.0_DEVELOPMENT
+!/doc/2.0_DEVELOPMENT/
+/doc/2.0_DEVELOPMENT/*
+
+!/doc/2.0_DEVELOPMENT/2.1_VERSIONING
+!/doc/2.0_DEVELOPMENT/2.3_EXTENSIONS
+!/doc/2.0_DEVELOPMENT/2.5_LANGUAGE
+!/doc/2.0_DEVELOPMENT/2.7_LIBRARIES
 
 # /engine
 !/engine/
@@ -73,6 +81,20 @@
 !/src/main.gdextension
 !/src/main.h
 
+# /src/filesize
+!/src/filesize
+/src/filesize/*
+
+!/src/filesize/size.c
+!/src/filesize/
+
+# /src/logging
+!/src/logging
+/src/logging/*
+
+!/src/logging/logging.c
+!/src/logging/logging.h
+
 # /src/init
 !/src/init
 /src/init/*