Ignore generated *.xmpi files

Source: https://texdoc.net/pkg/xmpincl -> page 3:

> basically create a new file .xmpi

TeX.gitignore

@@ -198,6 +198,9 @@ pythontex-files-*/
 # easy-todo
 *.lod
 
+# xmpincl
+*.xmpi
+
 # xindy
 *.xdy