Added MarkdownImage component (#6774)

* Added MarkdownImage component

* Fixed unit tests

webapp/tests/utils/formatting_imgs.test.jsx

@@ -9,7 +9,7 @@ describe('Markdown.Imgs', function() {
     it('Inline mage', function(done) {
         assert.equal(
             Markdown.format('![Mattermost](/images/icon.png)').trim(),
-            '<p><img src="/images/icon.png" alt="Mattermost" onload="window.markdownImageLoaded(this)" onerror="window.markdownImageLoaded(this)" class="markdown-inline-img"></p>'
+            '<p><img src="/images/icon.png" alt="Mattermost" class="markdown-inline-img"></p>'
         );
 
         done();
@@ -18,7 +18,7 @@ describe('Markdown.Imgs', function() {
     it('Image with hover text', function(done) {
         assert.equal(
             Markdown.format('![Mattermost](/images/icon.png "Mattermost Icon")').trim(),
-            '<p><img src="/images/icon.png" alt="Mattermost" title="Mattermost Icon" onload="window.markdownImageLoaded(this)" onerror="window.markdownImageLoaded(this)" class="markdown-inline-img"></p>'
+            '<p><img src="/images/icon.png" alt="Mattermost" title="Mattermost Icon" class="markdown-inline-img"></p>'
         );
 
         done();
@@ -27,7 +27,7 @@ describe('Markdown.Imgs', function() {
     it('Image with link', function(done) {
         assert.equal(
             Markdown.format('[![Mattermost](../../images/icon-76x76.png)](https://github.com/mattermost/platform)').trim(),
-            '<p><a class="theme markdown__link" href="https://github.com/mattermost/platform" rel="noreferrer" target="_blank"><img src="../../images/icon-76x76.png" alt="Mattermost" onload="window.markdownImageLoaded(this)" onerror="window.markdownImageLoaded(this)" class="markdown-inline-img"></a></p>'
+            '<p><a class="theme markdown__link" href="https://github.com/mattermost/platform" rel="noreferrer" target="_blank"><img src="../../images/icon-76x76.png" alt="Mattermost" class="markdown-inline-img"></a></p>'
         );
 
         done();
@@ -36,7 +36,7 @@ describe('Markdown.Imgs', function() {
     it('Image with width and height', function(done) {
         assert.equal(
             Markdown.format('![Mattermost](../../images/icon-76x76.png =50x76 "Mattermost Icon")').trim(),
-            '<p><img src="../../images/icon-76x76.png" alt="Mattermost" title="Mattermost Icon" width="50" height="76" onload="window.markdownImageLoaded(this)" onerror="window.markdownImageLoaded(this)" class="markdown-inline-img"></p>'
+            '<p><img src="../../images/icon-76x76.png" alt="Mattermost" title="Mattermost Icon" width="50" height="76" class="markdown-inline-img"></p>'
         );
 
         done();
@@ -45,7 +45,7 @@ describe('Markdown.Imgs', function() {
     it('Image with width', function(done) {
         assert.equal(
             Markdown.format('![Mattermost](../../images/icon-76x76.png =50 "Mattermost Icon")').trim(),
-            '<p><img src="../../images/icon-76x76.png" alt="Mattermost" title="Mattermost Icon" width="50" onload="window.markdownImageLoaded(this)" onerror="window.markdownImageLoaded(this)" class="markdown-inline-img"></p>'
+            '<p><img src="../../images/icon-76x76.png" alt="Mattermost" title="Mattermost Icon" width="50" class="markdown-inline-img"></p>'
         );
 
         done();