Add instances of IsString (List Char) (#2756)

* Add instances of `IsString (List Char)`

* Don't also `isString` as an instance from `Data.List.Literals`

* Add changelog entry

* Whitespace fix

Author: rvs314

CHANGELOG.md

@@ -562,3 +562,8 @@ Additions to existing modules
   ```agda
   SortingAlgorithm.sort-↭ₛ : ∀ xs → sort xs Setoid.↭ xs
   ```
+
+* In `Data.List.Instances`:
+  ```agda
+  instance listIsString : IsString (List Char)
+  ```

src/Data/List/Instances.agda

@@ -16,6 +16,8 @@ import Data.List.Effectful.Transformer as Trans
   using (functor; applicative; monad; monadT)
 open import Data.List.Properties
   using (≡-dec)
+open import Data.List.Literals
+  using (isString)
 open import Data.List.Relation.Binary.Pointwise
   using (Pointwise)
 open import Data.List.Relation.Binary.Lex.NonStrict
@@ -42,6 +44,7 @@ instance
   listMonad = monad
   listMonadZero = monadZero
   listMonadPlus = monadPlus
+  listIsString = isString
   -- ListT
   listTFunctor = λ {f} {g} {M} {{inst}} → Trans.functor {f} {g} {M} inst
   listTApplicative = λ {f} {g} {M} {{inst}} → Trans.applicative {f} {g} {M} inst