Split example.org into separate files

... hopefully correctly

This will hopefully improve ease of developing (more granular test results) and
prepares us for adding example org->html renders for gh-pages

org/testdata/captions.org

@@ -0,0 +1,13 @@
+Anything can be captioned. Also captions are not real, correct captions but just a paragraph below the element (bothe wrapped into a div)
+
+#+CAPTION: captioned soure block
+#+BEGIN_SRC sh
+echo "i have a caption!"
+#+END_SRC
+
+#+CAPTION: captioned link (video in this case)
+[[my-video.mp4]]
+note that only that one line is captioned, not the whole paragraph
+
+#+CAPTION: not happening!
+also, normal text lines can't be captioned