Merge branch 'update-ui-guide--svgs' into 'master'

Update UI Guide with SVG guidelines

This addition to the guide is to provide some guidelines to UX designers when exporting SVGs. Please let me know if anything is unclear or if you any improvements so we can document it clearly for everyone.

cc / @hazelyang @cperessini @dimitrieh @connorshea @annabeldunstone @dzaporozhets 

## What are the relevant issue numbers?
https://gitlab.com/gitlab-org/gitlab-ee/issues/872

See merge request !5748

doc/development/ui_guide.md

@@ -47,6 +47,42 @@ information from database or file system
 * `rss` for rss/atom feed
 * `plus` for link or dropdown that lead to page where you create new object (For example new issue page)
 
+### SVGs
+
+When exporting SVGs, be sure to follow the following guidelines:
+
+1. Convert all strokes to outlines.
+2. Use pathfinder tools to combine overlapping paths and create compound paths.
+3. SVGs that are limited to one color should be exported without a fill color so the color can be set using CSS.
+4. Ensure that exported SVGs have been run through an [SVG cleaner](https://github.com/RazrFalcon/SVGCleaner) to remove unused elements and attributes.
+
+You can open your svg in a text editor to ensure that it is clean. 
+Incorrect files will look like this:
+
+```xml
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<svg width="16px" height="17px" viewBox="0 0 16 17" version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
+    <!-- Generator: Sketch 3.7.2 (28276) - http://www.bohemiancoding.com/sketch -->
+    <title>Group</title>
+    <desc>Created with Sketch.</desc>
+    <defs></defs>
+    <g id="Page-1" stroke="none" stroke-width="1" fill="none" fill-rule="evenodd">
+        <g id="Group" fill="#7E7C7C">
+            <path d="M15.1111,1 L0.8891,1 C0.3981,1 0.0001,1.446 0.0001,1.996 L0.0001,15.945 C0.0001,16.495 0.3981,16.941 0.8891,16.941 L15.1111,16.941 C15.6021,16.941 16.0001,16.495 16.0001,15.945 L16.0001,1.996 C16.0001,1.446 15.6021,1 15.1111,1 L15.1111,1 L15.1111,1 Z M14.0001,6.0002 L14.0001,14.949 L2.0001,14.949 L2.0001,6.0002 L14.0001,6.0002 Z M14.0001,4.0002 L14.0001,2.993 L2.0001,2.993 L2.0001,4.0002 L14.0001,4.0002 Z" id="Combined-Shape"></path>
+            <polygon id="Fill-11" points="3 2.0002 5 2.0002 5 0.0002 3 0.0002"></polygon>
+            <polygon id="Fill-16" points="11 2.0002 13 2.0002 13 0.0002 11 0.0002"></polygon>
+            <path d="M5.37709616,11.5511984 L6.92309616,12.7821984 C7.35112915,13.123019 7.97359761,13.0565604 8.32002627,12.6330535 L10.7740263,9.63305349 C11.1237073,9.20557058 11.0606364,8.57555475 10.6331535,8.22587373 C10.2056706,7.87619272 9.57565475,7.93926361 9.22597373,8.36674651 L6.77197373,11.3667465 L8.16890384,11.2176016 L6.62290384,9.98660159 C6.19085236,9.6425813 5.56172188,9.71394467 5.21770159,10.1459962 C4.8736813,10.5780476 4.94504467,11.2071781 5.37709616,11.5511984 L5.37709616,11.5511984 Z" id="Stroke-21"></path>
+        </g>
+    </g>
+</svg>
+```
+
+Correct file will look like this:
+
+```xml
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 17" enable-background="new 0 0 16 17"><path d="m15.1 1h-2.1v-1h-2v1h-6v-1h-2v1h-2.1c-.5 0-.9.5-.9 1v14c0 .6.4 1 .9 1h14.2c.5 0 .9-.4.9-1v-14c0-.5-.4-1-.9-1m-1.1 14h-12v-9h12v9m0-11h-12v-1h12v1"/><path d="m5.4 11.6l1.5 1.2c.4.3 1.1.3 1.4-.1l2.5-3c.3-.4.3-1.1-.1-1.4-.5-.4-1.1-.3-1.5.1l-1.8 2.2-.8-.6c-.4-.3-1.1-.3-1.4.2-.3.4-.3 1 .2 1.4"/></svg>
+```
+
 
 ## Buttons