.gitignore: add missing ignores

Ignore output files created by "make defconfig; make".

Signed-off-by: Bjørn Forsman <bjorn.forsman@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/docs/.gitignore b/docs/.gitignore
index 11d6163..3d1c5bd 100644
--- a/docs/.gitignore
+++ b/docs/.gitignore
@@ -1,4 +1,5 @@
 /busybox.1
 /BusyBox.html
+/busybox.net
 /BusyBox.txt
 /busybox.pod