added comments

ExtensionSystem.agda

@@ -32,8 +32,11 @@ ExtensionSystem→Monad {𝒞 = 𝒞} 𝐾 = record
     { F = T
     ; η = η'
     ; μ = μ'
+    -- M3
     ; identityˡ = Identityˡ
+    -- M2
     ; identityʳ = K2
+    -- M1
     ; assoc = assoc'
     ; sym-assoc = sym assoc'
     }
@@ -45,10 +48,12 @@ ExtensionSystem→Monad {𝒞 = 𝒞} 𝐾 = record
         T = RMonad⇒Functor 𝐾
         open Functor T renaming (F₁ to T₁)
         open Equiv
+        -- constructing the natural transformation η from the given family of morphisms 'unit' 
         η' = ntHelper {F = Id} {G = T} record
             { η = λ X → unit
             ; commute = λ {X} {Y} f → sym K2
             }
+        -- constructing the natural transformation μ
         μ' = ntHelper {F = T ∘F T} {G = T} record
             { η = λ X → (idC {A = T₀ X})ᵀ
             ; commute = λ {X} {Y} f → begin