build: warning about Vue esm-bundler flags

# Problem

When I debug the extension using the `Extension` launch config, the debug console shows this Vue warning:

```
Feature flags __VUE_OPTIONS_API__, __VUE_PROD_DEVTOOLS__ are not explicitly defined. You are running the esm-bundler build of Vue, which expects these compile-time feature flags to be globally injected via the bundler config in order to get better tree-shaking in the production bundle.

For more details, see https://link.vuejs.org/feature-flags.
```

# Expected behavior

Our build should set these flags so that (1) to avoid future confusion/noise about the purpose of the warning, and (2) to gain any potential performance benefits, if possible. Or confirm that we don't need to set these flags and that our build is already optimized.

Start with the Extension launch config and the build configuration, then consult the linked Vue feature-flags documentation to understand the warning. Verify whether the build injects __VUE_OPTIONS_API__ and __VUE_PROD_DEVTOOLS__; done means the warning is removed during Extension debugging or the issue is clearly confirmed unnecessary with the build rationale documented.

Written by the indexing model from the issue text.