ignore/types: add more Cython file types

From the [Cython file types](https://cython.readthedocs.io/en/latest/src/userguide/language_basics.html?highlight=pxi#cython-file-types) paragraph on the official docs:

> There are three file types in Cython:
>    The implementation files, carrying a .py or .pyx suffix.
>    The definition files, carrying a .pxd suffix.
>    The include files, carrying a .pxi suffix.

PR #1113

ignore/src/types.rs

@@ -128,7 +128,7 @@ const DEFAULT_TYPES: &'static [(&'static str, &'static [&'static str])] = &[
     ("cshtml", &["*.cshtml"]),
     ("css", &["*.css", "*.scss"]),
     ("csv", &["*.csv"]),
-    ("cython", &["*.pyx"]),
+    ("cython", &["*.pyx", "*.pxi", "*.pxd"]),
     ("dart", &["*.dart"]),
     ("d", &["*.d"]),
     ("dhall", &["*.dhall"]),