fix(prejoin): Fix CSS for prejoin page according to design

css/_premeeting-screens.scss

             font-weight: 300;
             justify-content: center;
             line-height: 24px;
+            margin-bottom: 16px;
 
             .url {
                 display: flex;
                 }
             }
 
+            .copy-meeting-text {
+                width: 266px;
+                white-space: nowrap;
+                overflow: hidden;
+                text-overflow: ellipsis;
+            }
+
             &:hover {
                 align-self: stretch;
             }
             border: 1px solid transparent;
             color: white;
             outline-width: 0;
-            padding: 20px;
+            padding: 8px 0;
             text-align: center;
+            width: 100%;
 
             &.focused {
                 border-bottom: 1px solid white;
             display: inline-block;
             font-size: 15px;
             line-height: 24px;
-            margin: 10px;
+            margin-top: 16px;
             padding: 7px 16px;
             position: relative;
             text-align: center;
             width: 286px;
-    
+
             &.primary {
                 background: #0376DA;
                 border: 1px solid #0376DA;
             }
-    
+
             &.secondary {
                 background: transparent;
                 border: 1px solid #5E6D7A;
             }
-    
+
             &.text {
                 width: auto;
                 font-size: 13px;
                 margin: 0;
                 padding: 0;
             }
-    
+
             &.disabled {
                 background: #5E6D7A;
                 border: 1px solid #5E6D7A;
                 color: #AFB6BC;
                 cursor: initial;
-    
+
                 .icon {
                     & > svg {
                         fill: #AFB6BC;
                     }
                 }
-    
+
                 .options {
                     border-left: 1px solid #AFB6BC;
                 }
         position: absolute;
         width: 100%;
     }
-}
+}

react/features/base/premeeting/components/web/CopyMeetingUrl.js

                 <div
                     className = { `url ${showLinkCopied ? 'done' : ''}` }
                     onClick = { _copyUrl } >
-                    { !showCopyLink && !showLinkCopied && url }
-                    { showCopyLink && t('prejoin.copyAndShare') }
-                    { showLinkCopied && t('prejoin.linkCopied') }
+                    <div className = 'copy-meeting-text'>
+                        { !showCopyLink && !showLinkCopied && url }
+                        { showCopyLink && t('prejoin.copyAndShare') }
+                        { showLinkCopied && t('prejoin.linkCopied') }
+                    </div>
                     <Icon
                         onClick = { _copyUrl }
                         size = { 24 }