Improve formatting of app/finders/README.md

app/finders/README.md

 # Finders
 
-This type of classes responsible for collectiong items based on different conditions.
+This type of classes responsible for collection items based on different conditions.
 To prevent lookup methods in models like this:
 
 ```ruby
@@ -19,4 +19,4 @@ Better use this:
 issues = IssuesFinder.new.execute(project, user, filter)
 ```
 
-It will help keep models thiner
+It will help keep models thiner.