Move SCSS variables for topic post width

Move SCSS variables for topic post width

This allows them to be re-used by other components, for example the upcoming review queue.

diff --git a/app/assets/stylesheets/common/foundation/variables.scss b/app/assets/stylesheets/common/foundation/variables.scss
index fe706f9..29e1ebb 100644
--- a/app/assets/stylesheets/common/foundation/variables.scss
+++ b/app/assets/stylesheets/common/foundation/variables.scss
@@ -10,6 +10,9 @@ $medium-width: 995px !default;
 $large-width: 1110px !default;
 
 $input-padding: 4px 10px;
+$topic-body-width: 690px;
+$topic-body-width-padding: 11px;
+$topic-avatar-width: 45px;
 
 // Brand color variables
 // --------------------------------------------------
diff --git a/app/assets/stylesheets/desktop/topic-post.scss b/app/assets/stylesheets/desktop/topic-post.scss
index a6d836b..0a742e0 100644
--- a/app/assets/stylesheets/desktop/topic-post.scss
+++ b/app/assets/stylesheets/desktop/topic-post.scss
@@ -633,9 +633,6 @@ blockquote {
 }
 
 // variables are used to calculate the width of .gap
-$topic-body-width: 690px;
-$topic-body-width-padding: 11px;
-$topic-avatar-width: 45px;
 .topic-body {
   width: calc(#{$topic-body-width} + (#{$topic-body-width-padding} * 2));
   float: left;

GitHub sha: ca03b2ff