Ui improvements (#6198)

* PLT-6306 - Post alignment in compact view

* PLT-6266 - Adjusting spacing for files (compact)

* PLT-6302 - Margins not equal for paragraphs in post

* PLT-6332 - FIxing inline images

* PLT-6134 - Fixing border on emoji picker

* PLT-6323 - Fixing UI for system console user list

* PLT-6375 - Updating emoji picker

* PLT-6327 - Updating more channel/user list

* PLT-6241 - Adding IE detection

* PLT-6332- Fixing inline markdown images

webapp/sass/layout/_post.scss

@@ -359,6 +359,11 @@
 }
 
 .post-create__container {
+    @include flex(0 0 auto);
+    background: $white;
+    width: 100%;
+    z-index: 1000;
+
     label {
         font-weight: normal;
     }