fix: Rename Handlebars and Nunjucks extension setting to "extend"

Author: engelfrost

packages/development-edition-engine-handlebars/patternlab-config.json

@@ -88,7 +88,7 @@
   ],
   "engines": {
     "handlebars": {
-      "helpers": "helpers/*.js"
+      "extend": "helpers/*.js"
     }
   }
 }

packages/engine-handlebars/README.md

@@ -21,7 +21,7 @@ To add custom [helpers](http://handlebarsjs.com/#helpers) or otherwise interact
     ...
     "engines": {
       "handlebars": {
-        "helpers": [
+        "extend": [
           "handlebars-helpers.js",
           "helpers/**/*.js"
         ]

packages/engine-handlebars/lib/engine_handlebars.js

@@ -143,7 +143,7 @@ const engine_handlebars = {
 
     try {
       // Look for helpers in the config
-      helpers = config.engines.handlebars.helpers;
+      helpers = config.engines.handlebars.extend;
 
       if (typeof helpers === 'string') {
         helpers = [helpers];

packages/engine-nunjucks/README.md

@@ -24,7 +24,7 @@ To add custom filters or make customizations to the nunjucks instance, add the f
     ...
     "engines": {
       "nunjucks": {
-        "extensions": [
+        "extend": [
           "nunjucks-extensions/*.js"
         ]
       }

packages/engine-nunjucks/lib/engine_nunjucks.js

@@ -154,7 +154,7 @@ const engine_nunjucks = {
 
     try {
       // Look for helpers in the config
-      extensions = config.engines.nunjucks.helpers;
+      extensions = config.engines.nunjucks.extend;
 
       if (typeof extensions === 'string') {
         extensions = [extensions];