chore: renamed early-access-header and added test file

Author: nadeem-cs

index.d.ts

@@ -55,7 +55,7 @@ export interface Config {
     live_preview?: LivePreview;
     plugins?: ContentstackPlugin[];
     fetchOptions?: FetchOptions;
-    ea_headers?: string[]
+    early_access_headers?: string[]
 }
 // Stack Config
 export interface StackConfig {

test/entry/find.js

@@ -20,6 +20,12 @@ test('Initalise the Contentstack Stack Instance', function(TC) {
     }, 1000);
 });
 
+test.only('early_access_headers in stack initialization', function (t) {
+    const stack = Contentstack.Stack({ ...init.stack, early_access_headers: ['newCDA', 'taxonomy'] });
+    t.equal(stack.headers['x-header-ea'], 'newCDA,taxonomy', 'Early access headers should be added');
+    t.end();
+});
+
 test('default .find()', function(assert) {
     var Query = Stack.ContentType(contentTypes.source).Query(),
         field = 'updated_at';