HTML: add warning to page when built with build-preview

Author: ascholerChemeketa

css/components/elements/_misc-content.scss

@@ -151,6 +151,16 @@ article.theorem-like .emphasis {
     font-style: oblique;
 }
 
+.preview-build-warning {
+  background-color: rgb(249, 240, 240);
+  border: 2px solid rgb(202, 38, 38);
+  border-radius: 2px;
+  color: #333;
+  padding: 10px;
+  margin: 10px 0;
+}
+
+
 /* Adapted from William Hammond (attributed to David Carlisle) */
 /* "mathjax-users" Google Group, 2015-12-27 */
 

xsl/pretext-html.xsl

@@ -11298,6 +11298,9 @@ along with MathBook XML.  If not, see <http://www.gnu.org/licenses/>.
                         </xsl:attribute>
                     </xsl:if>
                     <div id="ptx-content" class="ptx-content">
+                        <xsl:if test="$b-build-preview">
+                            <div class="preview-build-warning">Preview build. Links and knowls that cross pages may not function correctly.</div>
+                        </xsl:if>
                         <xsl:if test="$b-has-printout">
                             <xsl:apply-templates select="." mode="print-preview-header"/>
                         </xsl:if>