install lex yacc on gitpod (#246)

### What problem were solved in this pull request?

Problem:
gitpod开发环境中没有安装flex和yacc工具

### What is changed and how it works?
在gitpod中安装flex和bison，以及readline

.gitpod.yml

@@ -5,6 +5,6 @@ github:
 tasks:
   - name: install dependencies
     init: |
-      sudo apt install cmake -y
+      sudo apt install cmake flex bison texinfo libreadline-dev -y
       sudo bash build.sh init
       echo -e "\033[32m\nDependency installed successfully\033[0m"