chore(readme): use mermaid for the diagram

README.md

@@ -7,12 +7,29 @@ A general suffix automaton implementation in Rust.
 Python bindings and some utilities are also available.
 Please check out [`general-sam-py`](https://github.com/ModelTC/general-sam-py).
 
-|         [![the suffix automaton of abcbc][sam-of-abcbc]][sam-oi-wiki]          |
-| :----------------------------------------------------------------------------: |
-| The suffix automaton of abcbc, image from [后缀自动机 - OI Wiki][sam-oi-wiki]. |
+```mermaid
+flowchart LR
+  init((ε))
+  a((a))
+  b((b))
+  ab((ab))
+  bc(((bc)))
+  abc((abc))
+  abcb((abcb))
+  abcbc(((abcbc)))
+
+  init -- a --> a
+  init -- b --> b
+  a -- b --> ab
+  b -- c --> bc
+  init -- c --> bc
+  ab -- c --> abc
+  bc -- b --> abcb
+  abc -- b --> abcb
+  abcb -- c --> abcbc
+```
 
-[sam-of-abcbc]: https://oi-wiki.org/string/images/SAM/SA_suffix_links.svg
-[sam-oi-wiki]: https://oi-wiki.org/string/sam/
+> The suffix automaton of abcbc.
 
 ## Examples