Adds jsDoc comments and cleans up JS logic

[tif-calin]

Summary

• adds jsDoc comments. If you've used TypeScript before it's essentially that but as simple JS comments. IDEs pick up on it and use it to provide type information and additional comments (see screenshots)
• cleans up JS logic. This is a bit subjective but I found parts of it hard to parse and tried to update it to make more sense and be in line with professional js style guides like airbnb's JS linter
• updates the package-lock.json. The old one was generated with an older version of npm and it was recommended to update it

Screenshots

IDE picks up comments and parameter types

IDE provides autocomplete for available config properties

IDE provides typehints for available config properties

[tif-calin]

PS we could also add @example like

/**
 * @example  
 * ```
 * const arr = [34, 58, 12, 29, 2];
 * 
 * asciichart.plot(arr, {
 *   format: x => `${Math.round(x) / 100}%`
 * });
 * 
 * @example plot('foobar'.split('').map(c => c.charCodeAt(0))
 * ```
 */

Wow GitHub even has syntax highlighting for jsDoc comments. Wild