Convert code-blocks to literalincludes in ReadingAndWritingImageFiles.rst

[cary-ilm]

The example code in website/ReadingAndWritingImageFiles.rst should be moved to individual files in website/src and included in the documentation files via .. literalinclude::, and also included in website/src/all.cpp so that it get built by CMake for testing and validation. See the other uses of literalinclude as examples.

This task requires some basic familiarity with reStructuredText and sphinx but the concepts are easy to pick up from other examples. See Building the Website for how to test the formatting.

[MeghaS94]

I'll take a look at this for dev days.

[MeghaS94]

Just a clarifying question on this - There's about 34 code-blocks left in ReadingAndWritingImageFiles.rst, does that mean I'll need to add 34 new cpp files?
whenever possible, would it make sense to put code in the same cpp file, and reference what gets included in the rst files with the start-after and end-before directives?

[cary-ilm]

Whatever makes sense is fine, but start-after/end-after sounds like a good approach for the shorter code snippets sounds like a good approach!

[MeghaS94]

Leaving an update here - I've made most of the changes for this, I will submit a PR soon. Thanks for all the help, Cary!