split all_vendor.odin

create 3 files:
- all_vendor.odin : no specific OS
- all_vendor_directx.odin : directx vendor, windows-only
- all_vendor_stb.odin : stb vendor, windows and linux only

stb could technically be used on others OS. but it is shipped upstream as set of c-files without unified library name.

examples/all/all_vendor_stl.odin

@@ -0,0 +1,15 @@
+//+build windows, linux
+package all
+
+import stb_easy_font "vendor:stb/easy_font"
+import stbi          "vendor:stb/image"
+import stbrp         "vendor:stb/rect_pack"
+import stbtt         "vendor:stb/truetype"
+import stb_vorbis    "vendor:stb/vorbis"
+
+_ :: stb_easy_font
+_ :: stbi
+_ :: stbrp
+_ :: stbtt
+_ :: stb_vorbis
+