feat: construct EXT_LIST from a config file

[logic-finder]

Currently, the pre-commit hook takes the extension list when it is built, i.e. make hook EXT_LIST='...'. However, I find that this way is a little inconvenient and error-prone. In light of this problem, an introduction of a configuration file would suffice to address the situation.

I didn't think much of the syntax of the config file as of now, but I think it would be fine with that of an INI file. For example,

[build]
   extlist = .c .h .as .js
   shutup = true