Make docs link to scalars consistent with other types

Author: spawnia

docs/type-definitions/index.md

@@ -4,16 +4,16 @@ graphql-php represents a **type** as a class instance from the `GraphQL\Type\Def
 - [`InterfaceType`](interfaces.md)
 - [`UnionType`](unions.md)
 - [`InputObjectType`](inputs.md)
-- [`ScalarType`](scalar-types.md)
+- [`ScalarType`](scalars.md)
 - [`EnumType`](enums.md)
 
 # Input vs. Output Types
 All types in GraphQL are of two categories: **input** and **output**.
 
-* **Output** types (or field types) are: [Scalar](scalar-types.md), [Enum](enums.md), [Object](object-types.md),
+* **Output** types (or field types) are: [Scalar](scalars.md), [Enum](enums.md), [Object](object-types.md),
   [Interface](interfaces.md), [Union](unions.md)
 
-* **Input** types (or argument types) are: [Scalar](scalar-types.md), [Enum](enums.md), [Inputs](inputs.md)
+* **Input** types (or argument types) are: [Scalar](scalars.md), [Enum](enums.md), [Inputs](inputs.md)
 
 Obviously, [NonNull and List](lists-and-nonnulls.md) types belong to both categories depending on their
 inner type.

docs/type-definitions/scalar-types.md renamed to docs/type-definitions/scalars.md

@@ -14,7 +14,7 @@ nav:
 - Type Definitions:
   - Introduction: type-definitions/index.md
   - Object Types: type-definitions/object-types.md
-  - Scalars: type-definitions/scalar-types.md
+  - Scalars: type-definitions/scalars.md
   - Enums: type-definitions/enums.md
   - Lists and Non-Nulls: type-definitions/lists-and-nonnulls.md
   - Interfaces: type-definitions/interfaces.md