fix(types): add Promise signature for bundleRenderer.renderToString (#7098)
fix(types): add Promise signature for bundleRenderer.renderToString (#7098)

* Make callback optional when providing context

Otherwise TypeScript compiler complains about `not assignable to parameter of type 'RenderCallback'`

* Update index.d.ts

Kingwl/vue,cnchanning/vue,Hanks10100/vue,cnchanning/vue,Jinjiang/vue,KingMario/vue,Jinjiang/vue,Hanks10100/vue,vuejs/vue,Kingwl/vue,cnchanning/vue,KingMario/vue,KingMario/vue,vuejs/vue,KingMario/vue,Kingwl/vue,vuejs/vue,Jinjiang/vue,vuejs/vue,Hanks10100/vue,Jinjiang/vue,Hanks10100/vue,Kingwl/vue