add link view for bubble theme

closes slab#857

assets/bubble.styl

@@ -9,3 +9,37 @@ textColor = #fff
 @import './core'
 @import './base'
 @import './bubble/*'
+
+.ql-container.ql-bubble:not(.ql-disabled)
+  a
+    position: relative
+    white-space: nowrap
+  a::before
+    background-color: #444
+    border-radius: 15px
+    top: -5px
+    font-size: 12px
+    color: #fff
+    content: attr(href)
+    font-weight: normal
+    overflow: hidden
+    padding: 5px 15px
+    text-decoration: none
+    z-index: 1
+  a::after
+    border-top: 6px solid #444
+    border-left: 6px solid transparent
+    border-right: 6px solid transparent
+    top: 0
+    content: " "
+    height: 0
+    width: 0
+  a::before, a::after
+    left: 0
+    margin-left: 50%
+    position: absolute
+    transform: translate(-50%, -100%)
+    transition: visibility 0s ease 200ms
+    visibility: hidden
+  a:hover::before, a:hover::after
+    visibility: visible