Bump react and react-dom to v19

[ebroder]

I think that the reason Dependabot's upgrade didn't work is because it only upgraded react without also upgrading react-dom, so add a rule to upgrade both at the same time in the future.

Supersedes #2562

[ebroder]

Meh I can fix most of the type errors, but slate-react needs updating for React 19:

node_modules/slate-react/dist/components/text.d.ts:8:59 - error TS2503: Cannot find namespace 'JSX'.

8     renderPlaceholder: (props: RenderPlaceholderProps) => JSX.Element;
                                                            ~~~

node_modules/slate-react/dist/components/text.d.ts:9:47 - error TS2503: Cannot find namespace 'JSX'.

9     renderLeaf?: ((props: RenderLeafProps) => JSX.Element) | undefined;
                                                ~~~

node_modules/slate-react/dist/components/text.d.ts:10:47 - error TS2503: Cannot find namespace 'JSX'.

10     renderText?: ((props: RenderTextProps) => JSX.Element) | undefined;
                                                 ~~~

so I think this is stuck for the moment.