bump crengine and others, adds HTML extended debug view (#5219)

Bump crengine: background image and other fixes:
- View HTML: option to show text unicode codepoints
- Fix attribute parsing: decode &-encoded chars
- Text: allow wrap after more unicode spaces and hyphen
- Fix: no left hanging when hanging punctuation disabled
- lvtextfm.cpp: more comments, some formatting cleanup
- Optimize background image drawing
- CSS: fix background-image file path resolution

Bump luasec to 0.8.1
Bump harfbuzz to 2.6.0

cre.cpp:
Adds setBackgroundImage() proxy function to crengine
facility to set background textures (this is unrelated
to the background-image CSS fixes).
No frontend code (yet) to select such an image.

View HTML: adds a 3rd view (extended debug view), showing the
unicode codepoint of each char and crengine rendereing methods.

frontend/document/credocument.lua

@@ -782,6 +782,11 @@ function CreDocument:setStatusLineProp(prop)
     self._document:setStringProperty("window.status.line", prop)
 end
 
+function CreDocument:setBackgroundImage(img_path) -- use nil to unset
+    logger.dbg("CreDocument: set background image", img_path)
+    self._document:setBackgroundImage(img_path)
+end
+
 function CreDocument:findText(pattern, origin, reverse, caseInsensitive)
     logger.dbg("CreDocument: find text", pattern, origin, reverse, caseInsensitive)
     return self._document:findText(