Turn _ into \_ in introduction.tex in documentation

[callegar]

Prerequisites

• Put an X between the brackets on this line if you have done all of the following:
  • Check that you are using the latest version of kaobook.
  • Check that your issue isn't already filed: https://github.com/fmarotta/kaobook/issues

Description

Documentation does not compile cleanly. In file examples/documentation/chapters/introduction.tex you have \Path{./examples/minimal_book/main.tex} which should be \Path{./examples/minimal\_book/main.tex} because this is not a verbatim env.

[fmarotta]

Fixed, thank you!