Started attempt at formalising component system used in BookStack

Added a document to try to define things.
Updated the loading so components are registed dynamically.
Added some standardised ways to reference other elems & define options

dev/docs/components.md

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+# JavaScript Components
+
+This document details the format for JavaScript components in BookStack.
+
+#### Defining a Component in JS
+
+```js
+class Dropdown {
+    setup() {
+    }
+}
+```
+
+#### Using a Component in HTML
+
+A component is used like so:
+
+```html
+<div component="dropdown"></div>
+
+<!-- or, for multiple -->
+
+<div components="dropdown image-picker"></div>
+```
+
+The names will be parsed and new component instance will be created if a matching name is found in the `components/index.js` componentMapping. 
+
+#### Element References
+
+Within a component you'll often need to refer to other element instances. This can be done like so:
+
+```html
+<div component="dropdown">
+    <span refs="dropdown@toggle othercomponent@handle">View more</span>
+</div>
+```
+
+You can then access the span element as `this.$refs.toggle` in your component.
+
+#### Component Options
+
+```html
+<div component="dropdown"
+    option:dropdown:delay="500"
+    option:dropdown:show>
+</div>
+```
+
+Will result with `this.$opts` being:
+
+```json
+{
+    "delay": "500",
+    "show": ""  
+}
+```