FR: strict mode

[fourstepper]

I just recently started using include-markdown more and found that it's great for composable snippets in documentation - thank you for the tool!

One thing I have encountered, though, is that mkdocs build goes through even though the referenced file path is wrong (e.g. the relative path doesn't lead anywhere). This can now cause silent breakage upon moving a part of the documentation elsewhere, instead of failing to build MkDocs

Would it be possible to add a configuration option to strictly fail the build if this happens?

Thank you!

[fourstepper]

Wow, thanks a lot, I really appreciate the quick "fix" (?) :)

Have a great day!