refactor: centralize envs and their defaults in modules/config (#464)

* feat(config): centralized env variables and their default values

* fix: fip `corsWildcard` variable check in `corsConfig`

* fix(config): use already declared variables and default some strings to undefined

* fix: check processingPriority against NaN

src/modules/processing/cookie/manager.js

@@ -1,9 +1,10 @@
 import Cookie from './cookie.js';
 import { readFile, writeFile } from 'fs/promises';
 import { parse as parseSetCookie, splitCookiesString } from 'set-cookie-parser';
+import { env } from '../../../modules/config.js'
 
 const WRITE_INTERVAL = 60000,
-      cookiePath = process.env.COOKIE_PATH,
+      cookiePath = env.cookiePath,
       COUNTER = Symbol('counter');
 
 let cookies = {}, dirty = false, intervalId;