refactor: move sources to lib

BREAKING CHANGE: moved sources

Sources have been moved to the `lib` folder. If you're referencing files
directly (`require(sql-highlight/index.js)`) you should instead
reference the new lib directory (`require(sql-highlight/lib/index.js)`)

Author: scriptcoded

index.test.js

@@ -1,4 +1,4 @@
-const { highlight } = require('./index')
+const { highlight } = require('./lib')
 
 const OPTIONS = {
   colors: {

index.js renamed to lib/index.js

@@ -7,6 +7,9 @@
     "type": "git",
     "url": "https://github.com/scriptcoded/sql-highlight.git"
   },
+  "files": [
+    "/lib"
+  ],
   "scripts": {
     "pretest": "npm run lint",
     "test": "jest",