Update skeleton extension .gitignore (#15738)

This adds:

- config.cache produced by: ./configure -C
- config.nice.bat, configure.js and configure.bat on Windows when using
  phpize

[skip ci]

ext/skeleton/.gitignore.in

@@ -6,16 +6,20 @@ acinclude.m4
 aclocal.m4
 autom4te.cache
 build
+config.cache
 config.guess
 config.h
 config.h.in
 config.log
 config.nice
+config.nice.bat
 config.status
 config.sub
 configure
 configure.ac
+configure.bat
 configure.in
+configure.js
 include
 install-sh
 libtool