[ADF-1586] Added files for core services (#2529)

* [ADF-1586] Added files for core services

* [ADF-1586] Fixed syntax error in example

docs/highlight.directive.md

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+# Highlight directive
+
+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>
+```
+
+## 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>
+```
+
+...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&gt; element around the
+selected text. The &lt;span&gt; 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>
+```
+
+<!-- Don't edit the See also section. Edit seeAlsoGraph.json and run config/generateSeeAlso.js -->
+<!-- seealso start -->
+## See also
+
+- [Text highlight pipe](text-highlight.pipe.md)
+- [Highlight transform service](highlight-transform.service.md)
+<!-- seealso end -->