Several bug fixes and improvements (#945)

* Update Dockerfile for code debugging.

* Format Python code using Black.

* Improve dark theme by defining html classes for the figures, animations and cover images.

* Fix several glossary translation.

* Update a code comment.

* Fix climbing_stairs_backtrack: the pruning should not require the sorted choices list.

* Update the code of array and list traversal.

* Fix a rendering issue of README.md

* Update code of list traversal.

* Fix array_definition.png

* Update README.md

* Fix max_capacity_moving_short_board.png

* Fix array.dart

* Fix array.dart

* Fix array.dart

* Fix array.dart

codes/Dockerfile

@@ -10,7 +10,7 @@ RUN apt-get update && apt-get install -y wget
 # Install languages environment
 ARG LANGS
 RUN for LANG in $LANGS; do \
-        case "$LANG" in \
+        case $LANG in \
             python) \
                 apt-get install -y python3.10 && \
                 update-alternatives --install /usr/bin/python python /usr/bin/python3.10 1 ;; \