fix(types): add optional environment SpaceLink to Sys interface (#920)

* fix(types): add optional environment SpaceLink to Sys interface

* fix(types): adjust link types and add EnvironmentLink

Co-authored-by: Janko Marklein <43542437+ruderngespra@users.noreply.github.com>
Co-authored-by: Janko Marklein <janko.marklein@contentful.com>

index.d.ts

@@ -159,23 +159,26 @@ export interface Sys {
     space?: {
         sys: SpaceLink;
     };
+    environment?: {
+        sys: EnvironmentLink;
+    };
     contentType: {
         sys: ContentTypeLink;
     };
 }
 
-export interface SpaceLink {
-    type: 'Link';
-    linkType: 'Space';
-    id: string;
-}
+export type LinkType = 'Space' | 'ContentType' | 'Environment'
 
-export interface ContentTypeLink {
-    type: 'Link';
-    linkType: 'ContentType';
-    id: string;
+export interface Link<T extends LinkType> {
+  type: 'Link'
+  linkType: T
+  id: string
 }
 
+export type SpaceLink = Link<'Space'>
+export type EnvironmentLink = Link<'Environment'>
+export type ContentTypeLink = Link<'ContentType'>
+
 export interface Field {
     disabled: boolean;
     id: string;