Add codespell ignore list and rc file

Author: ClausKlein

.codespellrc

@@ -0,0 +1,6 @@
+[codespell]
+builtin = clear,rare,en-GB_to_en-US,names,informal,code
+check-hidden =
+skip = ./.git,./build/*,./stagedir/*,*.log,.*.swp,*~,*.bak,Makefile
+quiet-level = 2
+# ignore-words = .ignore-words

Makefile

@@ -80,7 +80,7 @@ check:
 	done | tsort > /dev/null
 
 codespell:
-	codespell -L statics
+	codespell -L statics,snd,copyable,cancelled
 
 todo:
 	bin/mk-todo.py