[ADF-4152] Updated folder structure of core docs (#4415)

* [ADF-4152] Moved core library docs into subfolders

* [ADF-4152] Moved core library docs into subfolders

* [ADF-4152] Manual fixes to core doc file links

* [ADF-4152] Further automatic + manual link tidying

docs/core/directives/highlight.directive.md

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+---
+Title: Highlight directive
+Added: v2.0.0
+Status: Active
+Last reviewed: 2018-11-20
+---
+
+# [Highlight directive](../../../lib/core/directives/highlight.directive.ts "Defined in highlight.directive.ts")
+
+Adds highlighting to selected sections of an HTML element's content.
+
+## Basic Usage
+
+```HTML
+<div
+    [adf-highlight]="dance"
+    adf-highlight-selector=".highlightable"
+    adf-highlight-class="greenHighlight"
+>
+    <div class="highlightable">You can dance if you want to</div>
+</div>
+```
+
+## Class members
+
+### Properties
+
+| Name | Type | Default value | Description |
+| ---- | ---- | ------------- | ----------- |
+| classToApply | `string` | "adf-highlight" | CSS class used to apply highlighting. |
+| search | `string` | "" | Text to highlight. |
+| selector | `string` | "" | Class selector for highlightable elements. |
+
+## Details
+
+Add `adf-highlight` with a search term to an element to highlight occurrences
+of that term in its content. For example:
+
+```HTML
+<div [adf-highlight]="'dance'" adf-highlight-selector=".highlightable">
+    <div class="highlightable">
+        You can dance if you want to
+    </div>
+</div>
+```
+
+This will result in the word "dance" being highlighted. Note that you must also
+specify `adf-highlight-selector`, a CSS selector that specifies which
+elements can have their contents highlighted.
+
+If the search string contain spaces then each section between the spaces will
+be treated as a separate item to highlight. For example, you could use this to
+highlight all occurrences of words in a list.
+
+The highlighting works by adding an HTML &lt;span> element around the
+selected text. The &lt;span> includes a CSS class; this defaults to
+"adf-highlight" but you can supply your own class using the `adf-highlight-class`
+property:
+
+```HTML
+<div
+    [adf-highlight]="'dance'"
+    adf-highlight-selector=".highlightable"
+    adf-highlight-class="myGreenHighlight">
+    <div class="highlightable">
+        You can dance if you want to
+    </div>
+</div>
+```
+
+## See also
+
+-   [Text highlight pipe](../pipes/text-highlight.pipe.md)
+-   [Highlight transform service](../services/highlight-transform.service.md)