Wikipedia EPUBs: keep original float left/right in web mode

Previous cleanup resurrected multiple class names, so
we know now the original alignment of a float.
Use them in 'web' mode, as it allows floats to be nearer
the section they are refering to, and it may limit
floats truncation in page splitting.
But keep floats aligned on a single side in 'book' mode,
as it might allow easier reading.

frontend/ui/wikipedia.lua

@@ -1030,6 +1030,20 @@ body > div:dir(rtl) > div.thumb { /* invert if RTL */
         clear: left;
         margin:  0 0.5em 0.2em 0 !important;
 }
+/* Allow original mix of left/right floats in web mode */
+body > div > div.thumb.tleft {
+    -cr-only-if: float-floatboxes allow-style-w-h-absolute-units;
+        float: left !important;
+        clear: left;
+        margin:  0 0.5em 0.2em 0 !important;
+}
+body > div > div.thumb.tright {
+    -cr-only-if: float-floatboxes allow-style-w-h-absolute-units;
+        float: right !important;
+        clear: right;
+        margin:  0 0 0.2em 0.5em !important;
+}
+
 body > div > div.thumb img {
     /* Make float's inner images 100% of their container's width when not in "web" mode */
     -cr-only-if: float-floatboxes -allow-style-w-h-absolute-units;