Update README

README.md

@@ -16,6 +16,7 @@ usually marked with `???`. Lectures not listed here are not migrated to Scala
 | 2: Functional Data Structures   | [`datastructures`](src/main/scala/datastructures)                 | `testOnly datastructures.*`
 | 3: Error Handling               | [`errors`](src/main/scala/errors)                                 | `testOnly errors.*`
 | 4: Laziness                     | [`laziness`](src/main/scala/laziness/)                            | `testOnly laziness.*`
+| 5: Algebras, Laws and monoids   | [`algebra`](src/main/scala/algebra  /)                            | `testOnly algebra.*`
 
 ## Usage tips:
 To keep your local solutions to the exercises when pulling from the repository,