config: add js

Just like the config allows setting css URL path,
add a config for setting the js URL path

Setting the js path to an empty string disables
emitting the reference to it in the head section.

Signed-off-by: Andy Green <andy@warmcat.com>
Reviewed-by: John Keeping <john@keeping.me.uk>
diff --git a/Makefile b/Makefile
index 137150c..de7e13e 100644
--- a/Makefile
+++ b/Makefile
@@ -87,6 +87,7 @@
 	$(INSTALL) -m 0755 cgit $(DESTDIR)$(CGIT_SCRIPT_PATH)/$(CGIT_SCRIPT_NAME)
 	$(INSTALL) -m 0755 -d $(DESTDIR)$(CGIT_DATA_PATH)
 	$(INSTALL) -m 0644 cgit.css $(DESTDIR)$(CGIT_DATA_PATH)/cgit.css
+	$(INSTALL) -m 0644 cgit.js $(DESTDIR)$(CGIT_DATA_PATH)/cgit.js
 	$(INSTALL) -m 0644 cgit.png $(DESTDIR)$(CGIT_DATA_PATH)/cgit.png
 	$(INSTALL) -m 0644 favicon.ico $(DESTDIR)$(CGIT_DATA_PATH)/favicon.ico
 	$(INSTALL) -m 0644 robots.txt $(DESTDIR)$(CGIT_DATA_PATH)/robots.txt