add: mattermost (#243)

Using official EPS template from 2016 downloaded from https://www.mattermost.org/.

README.md

@@ -80,6 +80,7 @@ Say thanks!
 <td>Viber<br><img src="https://edent.github.io/SuperTinyIcons/images/svg/viber.svg" width="125" title="Viber" /><br>719 Bytes</td>
 <td>Mailchimp<br><img src="https://edent.github.io/SuperTinyIcons/images/svg/mailchimp.svg" width="125" title="Mailchimp" /><br>1010 Bytes</td>
 <td>Threema<br><img src="images/svg/threema.svg" width="125" title="Threema" /><br>774 Bytes</td>
+<td>Mattermost<br><img src="images/svg/mattermost.svg" width="125" title="Mattermost"/><br>621 Bytes</td>
 </tr>
 </table>
 

images/android-vector-drawable/mattermost.xml

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="utf-8"?>
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="512dp"
+    android:height="512dp"
+    android:viewportWidth="512"
+    android:viewportHeight="512">
+
+    <path
+        android:fillColor="#fff"
+        android:pathData="M 15 0 L 497 0 Q 512 0 512 15 L 512 497 Q 512 512 497 512 L 15 512 Q 0 512 0 497 L 0 15 Q 0 0 15 0 Z" />
+    <path
+        android:fillColor="#000000"
+        android:pathData="M429.6 174.4a190 190 0 0 0-55.3-69.8l2 41.2 2.2 2.9a141.3 141.3 0 0 1 25.3 113.6 144.8 144.8 0 0 1-179 112.7C153 357 105 283.4 118.6 210.6c10.7-57.5 44.7-95.8 99.9-115.2l2-0.8 1.6-1.2 20.1-29A190.9 190.9 0 0 0 65 237.5a191.5 191.5 0 0 0 152.4 206.1 191.2 191.2 0 0 0 222-132c14.3-46.7 11-92.8-9.7-137.3zm-236 61.7a69.7 69.7 0 0 0 78.5 62.4 70 70 0 0 0 60.3-81.3c-5.7-30.2-12.1-60.3-18.2-90.4l-7.8-38.1-2 1.7-40.2 39.5-49 48a68.1 68.1 0 0 0-21.5 58.2z" />
+</vector>

images/reference/index.md

@@ -166,3 +166,4 @@ Where possible this links to the organisation's brand guidelines page.
 | <img src="/images/svg/coffeescript.svg" width="256" /> | <img src="/images/reference/coffeescript-logo.svg" width="256" />  | http://coffeescript.org/ |
 | <img src="/images/svg/threema.svg" width="256" /> | <img src="/images/reference/threema.png" width="256" />  | https://threema.ch/press-files/5_graphics/1_icons_and_logos.zip |
 | <img src="/images/svg/print.svg" width="256" /> | <img src="/images/reference/print.svg" width="256" />  | https://www.iconfinder.com/icons/326675/print_icon#size=512 |
+| <img src="/images/svg/mattermost.svg" width="256" /> | <img src="/images/reference/mattermost.png" width="256" />  | https://www.mattermost.org/brand-guidelines/ |

images/svg/mattermost.svg

@@ -0,0 +1,7 @@
+<svg
+xmlns="http://www.w3.org/2000/svg"
+aria-label="Mattermost"
+role="img" viewBox="0 0 512 512">
+<rect width="512" height="512" rx="15%" fill="#fff"/>
+<path d="M429.6 174.4a190 190 0 0 0-55.3-69.8l2 41.2 2.2 2.9a141.3 141.3 0 0 1 25.3 113.6 144.8 144.8 0 0 1-179 112.7C153 357 105 283.4 118.6 210.6c10.7-57.5 44.7-95.8 99.9-115.2l2-.8 1.6-1.2 20.1-29A190.9 190.9 0 0 0 65 237.5a191.5 191.5 0 0 0 152.4 206.1 191.2 191.2 0 0 0 222-132c14.3-46.7 11-92.8-9.7-137.3zm-236 61.7a69.7 69.7 0 0 0 78.5 62.4 70 70 0 0 0 60.3-81.3c-5.7-30.2-12.1-60.3-18.2-90.4l-7.8-38.1-2 1.7-40.2 39.5-49 48a68.1 68.1 0 0 0-21.5 58.2z"/>
+</svg>