chore: declare packages as side-effect free

[devtechedge]

Closes #2627.

This declares sideEffects so webpack, Rollup and esbuild can drop unused modules.

core, react, material-renderers, vanilla-renderers, angular, angular-material and vue get "sideEffects": false.

vue-vanilla and vue-vuetify get "sideEffects": ["*.css"] instead.

Their READMEs tell users to import @jsonforms/vue-vanilla/vanilla.css and @jsonforms/vue-vuetify/lib/jsonforms-vue-vuetify.css, and a plain false lets webpack drop those imports.

A throwaway webpack probe kept both stylesheets with *.css, including the nested vuetify file, and dropped both when the field was false.

dayjs.extend runs at module scope in material-renderers, vue-vuetify and angular-material.

Nothing imports those modules bare, and each package ships one bundle, so that setup stays when a renderer is actually used.

ng-packagr copies sideEffects: false into the built lib/package.json for both Angular packages, so the published manifest and the build output match.

pnpm i --frozen-lockfile, pnpm build, pnpm test and pnpm run build:examples-app passed.

npm pack on core, angular, vue-vanilla and vue-vuetify includes the field.

An esbuild probe dropped an unused @jsonforms/core import (about 50KB down to the entry) and kept the module when the field was absent.

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