12 Modify build settings

[mst101]

Previously the IIFE and UMD builds were being overwritten by non-minified versions when the ESM build was run.

This prevents that from happening and simplifies the build process by having:

• scripts/build/default.js create minified versions of the .iife.js and .umd.cjs files
• scripts/build/modules.js create unminifed versions of the .cjs and .mjs files.

It also points the unpkg CDN to the newly named dist/vue-datepicker.umd.cjs file.