.gitignore: Add file

Ignore everything new by default.

This avoids having to update the .gitignore when we need to ignore
something new.  It also avoids accidents that may add an unwanted
temporary file.

Cc: Debian man-pages <manpages@packages.debian.org>
Cc: Dr. Tobias Quathamer <toddy@debian.org>
Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

.gitignore

@@ -0,0 +1,13 @@
+# Ignore everything new by default
+/*
+
+# Ignore everything in man?/ that doesn't follow conventions (e.g., tmp files)
+!/man?/
+/man?/**
+!/man?/**.?
+
+# These files change name in each release
+!/man-pages*.Announce
+!/man-pages*.lsm
+
+!/scripts/