Started playing with prosemirror

- Got base setup together with WYSIWYG/Markdown switching, where HTML is
  the base content format.
- Added some testing routes/views for initial development.
- Added some dev npm tasks to support editor-specific actions.

resources/js/editor/schema.js

@@ -0,0 +1,10 @@
+import {Schema} from "prosemirror-model";
+import {schema as basicSchema} from "prosemirror-schema-basic";
+import {addListNodes} from "prosemirror-schema-list";
+
+const bookstackSchema = new Schema({
+    nodes: addListNodes(basicSchema.spec.nodes, "paragraph block*", "block"),
+    marks: basicSchema.spec.marks
+})
+
+export {bookstackSchema as schema};