Scope Data: Add keyword.declaration.import

An `import` keyword is closer to a declaration (for the local namespace)
than a "control keyword", where this was defined in previously.

However, until this sees more usage or it has been agreed upon by more
than two people/syntax definitions, I'm still keeping
`keyword.control.import`.

plugins/lib/scope_data/data.py

@@ -104,6 +104,7 @@
             function
             interface
             impl
+            import
             struct
             trait
             union