fix: altair did not work in jupyter notebook due to wrong mimetype

Because the vega url does not end with .js the CdnHandler does not serve the
file with the correct mimetype. We do not store the mime type on disk,
so we do not know the mimetype of the file.
Currently, the mimetype is guessed based on the file extension.
By giving a more explicit path that ends in .js, we can make sure the
mimetype is set correctly.
In the end this caused the Altair component not to work.

solara/widgets/vue/vegalite.vue

@@ -12,9 +12,9 @@ module.exports = {
         require.config({
             map: {
                 '*': {
-                    'vega': `${this.getCdn()}/vega@5`,
-                    'vega-lite': `${this.getCdn()}/[email protected]`,
-                    'vega-embed': `${this.getCdn()}/vega-embed@6`,
+                    'vega': `${this.getCdn()}/vega@5/build/vega.min.js`,
+                    'vega-lite': `${this.getCdn()}/[email protected]/build/vega-lite.min.js`,
+                    'vega-embed': `${this.getCdn()}/vega-embed@6/build/vega-embed.min.js`,
                 }
             }
         })