Figures revision and bug fixes (#1041)

* Revised the figures thoughout the book.

* Utilize roboto and roboto mono as the font faimly of the English edition

* Fix the naming style

* Update two figures.

* Fix margin of the hero image

* Fix margin of the hero image

docs/chapter_heap/build_heap.md

@@ -46,7 +46,7 @@ $$
 T(h) = 2^0h + 2^1(h-1) + 2^2(h-2) + \dots + 2^{(h-1)}\times1
 $$
 
-化简上式需要借助中学的数列知识，将对 $T(h)$ 乘以 $2$ ，得到：
+化简上式需要借助中学的数列知识，先将 $T(h)$ 乘以 $2$ ，得到：
 
 $$
 \begin{aligned}