DOC: Fix typos in different subsections of the documentation

Fix typos found in the design-thoughts, internals and lua-api
subsections of the documentation.
diff --git a/doc/design-thoughts/rate-shaping.txt b/doc/design-thoughts/rate-shaping.txt
index 255ae4a..ca09408 100644
--- a/doc/design-thoughts/rate-shaping.txt
+++ b/doc/design-thoughts/rate-shaping.txt
@@ -63,7 +63,7 @@
    - 1 list of rule-based checkpoints per backend
    - 1 list of rule-based checkpoints per server
 
-Each of these lists have a lot of rules conditionned by ACLs, just like the
+Each of these lists have a lot of rules conditioned by ACLs, just like the
 use-backend rules, except that all rules are evaluated in turn.
 
 Since we might sometimes just want to enable that without setting any limit and