Several bug fixes and improvements (#1178)

* Update pythontutor block with the latest code

* Move docs-en to en/docs

* Move mkdocs.yml and README to en folder

* Fix en/mkdocs.yml

* Update the landing page

* Fix the glossary

* Reduce the font size of the code block tabs

* Add Kotlin blocks to en/docs

* Fix the code link in en/.../deque.md

* Fix the EN README link

en/docs/chapter_data_structure/index.md

@@ -0,0 +1,13 @@
+# Data Structures
+
+<div class="center-table" markdown>
+
+![Data Structures](../assets/covers/chapter_data_structure.jpg)
+
+</div>
+
+!!! abstract
+
+    Data structures serve as a robust and diverse framework.
+
+    They offer a blueprint for the orderly organization of data, upon which algorithms come to life.