Fix exports of ogv-support.js/ogv-version.js + some JS build clean-up

[Mesoptier]

The main reason for this PR is to fix the issue where the compiled ogv-support.js and ogv-version.js files don't actually export anything, where you'd expect the OGVCompat and OGVVersion exports. In fact, these files would only assign those values to the global object.

I've fixed this by specifying the output.library.type: 'umd' option for these entries in the webpack config. This will make the exports work as expected in AMD/CommonJS module environments.

Additionally, by omitting output.library.name, the exports will be assigned directly to the window object when loaded in a <script> tag. Therefore, I've also removed the explicit window-assignments from the main three entrypoints.

See also: https://webpack.js.org/configuration/output/#type-umd

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Other small changes to the JS build:

• Changed prepublish script to prepack, so make -j4 dist only runs before npm pack/npm publish and NOT for npm install. This might require a change in the README. If you disagree with this change, I suggest changing it to prepare instead as per https://docs.npmjs.com/cli/v9/using-npm/scripts#prepare-and-prepublish.
• NPM automatically updated package-lock.json after npm install.
• Updated Browserslist DB, see https://github.com/browserslist/update-db#why-you-need-to-call-it-regularly.
• Webpack mode is now specified per-script in package.json, allowing for development mode builds while developing.