Transpile @vector-im/compound-web with babel

[germain-gg]

Fixes #25905
For #25883

To review alongside matrix-org/matrix-react-sdk#11354

Checklist

• Tests written for new code (and old code if feasible)
• Linter and other CI checks pass
• Sign-off given on the changes (see CONTRIBUTING.md)

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This change is marked as an internal change (Task), so will not be included in the changelog.

[t3chguy]

@germain-gg could you include the rationale for this in the PR description? Why not just consume the built artifacts from the library like we do for the vast majority of our dependencies (both internal & external)

[germain-gg]

@t3chguy we essentially need it because it otherwise throws

2023-08-02 10:29:36.683 [element-js] ERROR in ../matrix-react-sdk/node_modules/@vector-im/compound-web/dist/compound-web.js 1482:22
2023-08-02 10:29:36.683 [element-js] Module parse failed: Unexpected token (1482:22)
2023-08-02 10:29:36.683 [element-js] You may need an appropriate loader to handle this file type, currently no loaders are configured to process this file. See https://webpack.js.org/concepts#loaders
2023-08-02 10:29:36.683 [element-js] |         onMouseDown: (e) => {
2023-08-02 10:29:36.683 [element-js] |           e.preventDefault();
2023-08-02 10:29:36.683 [element-js] >           onMouseDown?.(e);
2023-08-02 10:29:36.683 [element-js] |         }
2023-08-02 10:29:36.683 [element-js] |       },

We still use the ?. optional chaining operator in the original bundle because our browser support does not require us to transpile it, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Optional_chaining#browser_compatibility

But our webpack/babel setup is tricking us in having to do it anyway. And i'm not looking to fix this at this stage.

[t3chguy]

Could we be more specific, there might be transitive imports which also contain the text compound-web

[t3chguy]

LGTM