build: add vue-router.esm-browser.prod.js

[skirtles-code]

Based on #1847.

Currently we have vue-router.esm-browser.js, but there isn't a production version of that file.

The key benefits of the newly added vue-router.esm-browser.prod.js are:

1. It's minified.
2. It doesn't have a dependency on @vue/devtools-api.

That second point is important, as various CDNs can automatically apply the minification, but they can't strip out the dependency on @vue/devtools-api.

The moduleSideEffects: false setting is responsible for ensuring @vue/devtools-api is removed. Without that, we end up with import "@vue/devtools-api" in the built file. See https://rollupjs.org/configuration-options/#treeshake-modulesideeffects for details of that setting. While the setting is being applied to all builds, none of the other builds are actually impacted in practice.

Do we actually need a production build for esm-browser? Not sure, but based on the comments on #1847 and #2241, it does seem that some people would find it useful. An equivalent file is already provided by both Vue Router 3 and Vue core.

Closes #1847.

[netlify[bot]]

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[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 91.01%. Comparing base (d6d4dd3) to head (79f83dc). Report is 2 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2242 +/- ## ======================================= Coverage 91.01% 91.01% ======================================= Files 24 24 Lines 1135 1135 Branches 351 351 ======================================= Hits 1033 1033 Misses 63 63 Partials 39 39 ```

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