ignore/types: add Prolog file types

This improves the Prolog file type rules.

* `.pl` is the most common extension in the wild, though `.pro` is
   preferred in places where file extension may clash with Perl[1].
* `.P` is used for compatibility with XSB Prolog dialect[2].

PR #2590

[1]: https://www.swi-prolog.org/pldoc/man?section=fileext
[2]: https://www.swi-prolog.org/pldoc/man?section=xsb-source

crates/ignore/src/default_types.rs

@@ -201,6 +201,7 @@ pub const DEFAULT_TYPES: &[(&[&str], &[&str])] = &[
     (&["po"], &["*.po"]),
     (&["pod"], &["*.pod"]),
     (&["postscript"], &["*.eps", "*.ps"]),
+    (&["prolog"], &["*.pl", "*.pro", "*.prolog", "*.P"]),
     (&["protobuf"], &["*.proto"]),
     (&["ps"], &["*.cdxml", "*.ps1", "*.ps1xml", "*.psd1", "*.psm1"]),
     (&["puppet"], &["*.epp", "*.erb", "*.pp", "*.rb"]),