Add test functionality and fix small issues

Author: salmenf

README.md

@@ -1,5 +1,5 @@
-# Slides (`@webwriter/slides@2.1.0`)
-[License: MIT](LICENSE) | Version: 2.1.0
+# Slides (`@webwriter/slides@2.2.0`)
+[License: MIT](LICENSE) | Version: 2.2.0
 
 WIP - Present content as a sequence of screens (slides, tabs, etc.).
 
@@ -42,7 +42,7 @@ npm install @webwriter/slides
 | `activeSlideIndex` | `number` | Index of the active slide. | `0` | ✗ |
 | `activeSlide` | `WebwriterSlide` | Active slide element. | - | ✗ |
 | `hasNextSlide` | `boolean` | False if slideshow is on the last slide. | - | ✗ |
-| `hasPreviousSlide` | `boolean` | False if slideshow is on the last slide. | - | ✗ |
+| `hasPreviousSlide` | `boolean` | False if slideshow is on the first slide. | - | ✗ |
 
 *Fields including [properties](https://developer.mozilla.org/en-US/docs/Glossary/Property/JavaScript) and [attributes](https://developer.mozilla.org/en-US/docs/Glossary/Attribute) define the current state of the widget and offer customization options.*
 
@@ -126,4 +126,4 @@ npm install @webwriter/slides
 
 
 ---
-*Generated with @webwriter/build@1.4.0*
+*Generated with @webwriter/build@1.5.0*

custom-elements.json

@@ -17,6 +17,12 @@
             }
           ],
           "members": [
+            {
+              "kind": "field",
+              "name": "localize",
+              "privacy": "protected",
+              "default": "LOCALIZE"
+            },
             {
               "kind": "field",
               "name": "scopedElements",
@@ -105,7 +111,7 @@
               "type": {
                 "text": "boolean"
               },
-              "description": "False if slideshow is on the last slide.",
+              "description": "False if slideshow is on the first slide.",
               "readonly": true
             },
             {