opencv4nodejs not installing with "library dir does not exist" error

# Error Message
```
christopheryeemon@system76-pc:~$ npm i -g opencv4nodejs
npm ERR! code 1
npm ERR! path /home/christopheryeemon/.nvm/versions/node/v12.16.2/lib/node_modules/opencv4nodejs
npm ERR! command failed
npm ERR! command sh -c node ./install/install.js
npm ERR! info install using lib dir: /home/christopheryeemon/.nvm/versions/node/v12.16.2/lib/node_modules/opencv4nodejs/node_modules/opencv-build/opencv/build/lib
npm ERR! /home/christopheryeemon/.nvm/versions/node/v12.16.2/lib/node_modules/opencv4nodejs/install/install.js:37
npm ERR! throw new Error('library dir does not exist: ' + libDir)
npm ERR! ^
npm ERR!
npm ERR! Error: library dir does not exist: /home/christopheryeemon/.nvm/versions/node/v12.16.2/lib/node_modules/opencv4nodejs/node_modules/opencv-build/opencv/build/lib
npm ERR! at Object. (/home/christopheryeemon/.nvm/versions/node/v12.16.2/lib/node_modules/opencv4nodejs/install/install.js:37:9)
npm ERR! at Module._compile (internal/modules/cjs/loader.js:1156:30)
npm ERR! at Object.Module._extensions..js (internal/modules/cjs/loader.js:1176:10)
npm ERR! at Module.load (internal/modules/cjs/loader.js:1000:32)
npm ERR! at Function.Module._load (internal/modules/cjs/loader.js:899:14)
npm ERR! at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:74:12)
npm ERR! at internal/main/run_main_module.js:18:47

npm ERR! A complete log of this run can be found in:
npm ERR! /home/christopheryeemon/.npm/_logs/2021-06-25T22_50_09_267Z-debug.
```

*OpenCV version* (example 3.4.1): 5.6.0

*With OpenCV-contrib?* (extra modules): no

*OS*: Ubuntu 20.04.2 LTS