Clean up format-title build process

[nickrum]

In addition to the cleanups, this also increases the target version to ES2019 for all builds except the global one, it changes unpkg's default entrypoint to the esm one to align with the sdk and it bundles the types to a single file resulting in a tiny two-line declaration file.

The build process and the way the exports in package.json work is inspired by vue-next.

The secondary goal of this PR is to find a build config that can also be applied to the SDK. (ref #10053, cc @joselcvarela)

[joselcvarela]

Hey @nickrum
I don't know if you have tested this with some server side render framework but on #10053 I had trouble with .mjs file and Nuxt. I believe the cause is on VM module from Node.js
The solution was to remove the .mjs file and put export CJS file as default by setting main on package.json.

[nickrum]

@joselcvarela I didn't test this PR with a server side render framework specifically, but I did test the SDK with SvelteKit when I added the index.mjs file, not having any troubles. Which version of Nuxt were you using? Re-exporting the cjs entrypoint from a *.mjs file is very common and also recommended by node to prevent dual package hazards.

That's weird, with a recent version of Node, the main field should just be ignored. This PR doesn't even change the main field, though.