sdgui: rasterize some icons, including for Windows

README.adoc

@@ -28,10 +28,10 @@ The rest of this README will concern itself with externalities.
 
 Building and Running
 --------------------
-Build dependencies: CMake, pkg-config, asciidoctor +
+Build dependencies: CMake, pkg-config, asciidoctor, librsvg (for the GUI) +
 Runtime dependencies: ncursesw, zlib, ICU, termo (included), glib-2.0 >= 2.38,
  pango, xcb, xcb-xfixes (the latter two optional for the TUI),
- gtk+-3.0 (for the alternative graphical UI)
+ gtk+-3.0 (for the GUI)
 
  $ git clone --recursive https://git.janouch.name/p/sdtui.git
  $ mkdir sdtui/build