Enforce text cursor on compose box (#204)

In Chrome when the compose box is focused, only its padding has a text cursor, the containing `:before` element has a default cursor.

This does not apply in FF.

Alternatively you could define the text cursor for the `:before` element, but considering this would have to be set on all future child elements, setting it on the parent is prabably be more future proof.

src/sass/sections/_compose_area.scss

@@ -35,6 +35,7 @@
                     line-height: 1.3em;
                     max-height: calc(1.3em * 5);
                     min-height: 1.3em;
+                    cursor: text;
 
                     img {
                         vertical-align: middle;