Add markdown file detailing a testing script for the shading/flatfield correction method.

Author: rohangirishrao

tests/imagej/shading-test.md

@@ -0,0 +1,18 @@
+### ----------------------
+
+ The following code block is a `python` script to be used in a Fiji with the shading branch's .jar already pasted into ./jars in the Fiji installation
+
+ Recommended is to import an image you wish to test on (Shaded-blobs.png e.g) and then drag this script into Fiji and run it.
+ If a resulting image pops up (while using flatfield method), everything works finely.
+### ----------------------
+
+```python
+from imcflibs.imagej import shading
+# import imcflibs.imagej
+import ij
+from ij import IJ
+
+imp = IJ.getImage()
+imcf_shading = shading.simple_flatfield_correction(imp)
+# Or any other method in class shading
+imcf_shading.show()