Introduced 11ty

Set new version based on all changes since last version change, which was 0.4.2.

Removed obsolete devDependencies, now only using 11ty and sass.

Update to package.json fields

- New sass version
- Update to project links
- Rearranged fields
- New commands for 'scripts' that include changes from branch testing-npm-scripts
- Added field 'private' to prevent publishing by mistake

Added configuration for 11ty to reflect previous behaviour from gulp.

- Moved source/templates/demo/data.json to source/screens/demo.json so it can be used
- Fixed demo template so it can use the data source
- Removed source/data/demo.json which was not used

source/templates/demo/data.json

@@ -1,66 +0,0 @@
-{
-  "demoadditionallinks": [
-    {
-      "href": "demo.html",
-      "text": "Index"
-    },
-    {
-      "href": "demo/intro.html",
-      "text": "Intro"
-    },
-    {
-      "href": "demo/elements.html",
-      "text": "Elements"
-    },
-    {
-      "href": "demo/examples.html",
-      "text": "Examples"
-    }
-  ],
-  "demolinks": [
-    {
-      "href": "demo/blank.html",
-      "text": "Blank"
-    },
-    {
-      "href": "demo/card.html",
-      "text": "Card"
-    },
-    {
-      "href": "demo/portal.html",
-      "text": "Portal"
-    },
-    {
-      "href": "demo/maintenance.html",
-      "text": "Maintenance"
-    },
-    {
-      "href": "demo/error/304.html",
-      "text": "304"
-    },
-    {
-      "href": "demo/error/400.html",
-      "text": "400"
-    },
-    {
-      "href": "demo/error/401.html",
-      "text": "401"
-    },
-    {
-      "href": "demo/error/403.html",
-      "text": "403"
-    },
-    {
-      "href": "demo/error/404.html",
-      "text": "404"
-    },
-    {
-      "href": "demo/error/408.html",
-      "text": "408"
-    },
-    {
-      "href": "demo/error/500.html",
-      "text": "500"
-    }
-  ]
-}