case sensitive extension

[chicco785]

having a repository where - for whatever mystery - some files have .md and others .MD extension, i realised that the action is case sensitive. I was wondering if it is possible to extend the file-extension variable to support multiple extensions, this would allow to solve the issue and in general to support multiple extensions for markdown files.

[chicco785]

a quick patch for case insensitive support is replacing -name with -iname