F citation cff

Adding a citation.cff file, see: https://citation-file-format.github.io/

src/core/js/ext_bottom_line.js

@@ -68,6 +68,19 @@
  * @requires ext_table_preview (module from ext_table_preview.js)
  */
 
+/**
+  * Helper function analogous to ext_references isOutOfViewport
+  *
+  * Check whether the bottom of an entity is within the viewport.
+  * Returns true when this is the case and false otherwise.
+  *
+  */
+function is_bottom_in_viewport(entity) {
+    var bounding = entity.getBoundingClientRect();
+    return bounding.bottom > 0 && bounding.bottom < (window.innerHeight ||
+                                                     document.documentElement.clientHeight);
+}
+
 var ext_bottom_line = function($, logger, is_in_view_port, load_config, getEntityPath, connection, UTIF, ext_table_preview) {
 
     /**
@@ -568,7 +581,7 @@ var ext_bottom_line = function($, logger, is_in_view_port, load_config, getEntit
         BottomLineWarning: BottomLineWarning,
     }
 }($, log.getLogger("ext_bottom_line"),
-  resolve_references.is_in_viewport_vertically, load_config, getEntityPath,
+  is_bottom_in_viewport, load_config, getEntityPath,
   connection, UTIF, ext_table_preview);