Ignore files where just the "last updated" field was changed

[th-we]

Every commit will update all the documentation pages, but the only difference for most of them will be the "Last updated" field at the bottom of the page. If this is the only change, those files should be ignored and not be added to the amended commit.

Problem is that what is actually added there depends on the template, which is user configurable. Instead of checking for changed content, one could also check for changed Lua files with @module comment and add the corresponding documentation files. However, if a module was added/removed, then (again depending on the user configurable template) all documentation pages may have to be updated because the navigation <div> of all files changed.