test: add afl fuzzer

[Enter-tainer]

Usage

First prepare a bunch of tex input, I suggest the top 50 of oiwiki:

const test = require('./oiwiki-231222.json')
const fs = require('fs');
// write each test case to a file in a subdirectory

for (const [i, t] of test.entries()) {
  fs.writeFileSync(`./seed/${i}.txt`, t.text);
  if (i > 50) {
    break;
  }
}

Then build and fuzz

cargo afl build --bin fuzz-target-mitex
cargo afl fuzz -i local/seed -o local/fuzz-res ./target/debug/fuzz-target-mitex

To minimize test case, using afl-tmin

cargo afl tmin -i crash.tex -o minimized.tex ./target/debug/fuzz-target-mitex