Add therefor->therefore, therefor,

seems that `therefor` is a legit legal word. But I added this entry because most likely it's `therefore`

codespell_lib/data/dictionary.txt

diff --git a/codespell_lib/data/dictionary.txt b/codespell_lib/data/dictionary.txt
index 5966a3a..2667a52 100644
--- a/codespell_lib/data/dictionary.txt
+++ b/codespell_lib/data/dictionary.txt
@@ -4937,6 +4937,7 @@
 ther->there, their, the, other,
 therafter->thereafter
 therby->thereby
+therefor->therefore, therefor,
 therfore->therefore
 theri->their
 theshold->threshold