test: Initial unit testing

- Test quests vector loading
- Test default quest on empty fields
- Test correct quest
- Fixed config paths handling

tests/cfg/quests/1.toml

@@ -0,0 +1,8 @@
+# This example demonstrates typical quest
+# see main.rs
+id = 1
+difficulty = "Easy"
+reward = 100
+name = "Example easy quest"
+description = "Answer this quest without any attachments or comments"
+answer = "Accept the answer if it has no attachments and an empty comment"