Include more lines of qrcode svg to allow for embedded logos

Change-Id: If96e7a0764325088adbe8e32614f5273d6c24c9a
diff --git a/R/posterdown_html.R b/R/posterdown_html.R
index 8ac3ea5..8e54155 100644
--- a/R/posterdown_html.R
+++ b/R/posterdown_html.R
@@ -74,7 +74,7 @@
   }
   qrcode::generate_svg(qrcode, tmp,  show = FALSE)
   return(paste0( sprintf('<a class="qrcode" href="%s"><img class="qrcode">', url),
-                 gsub("\r?\n|\r", "", readChar(tmp, 1e5)),
+                 gsub("\r?\n|\r", "", readChar(tmp, 1e7)),
                  '</img></a>'
          ))
 }