fix several type and build errors and fix example type inference

[flybayer]

• Fix type of ChangeProps.onChange
• Fix basic react example <form.Subscribe> to get type inference working
• Fix build error by removing unused validateForm() method
• Fix the build by adding a few as any on react-store errors that I don't understand
• Fix the below pnpm test:build error by adding ['@babel/plugin-proposal-class-properties', { loose: false }] to the babel config

[!] Error: Private field '#prevState' must be declared in an enclosing class (Note that you need plugins to import files that are not JavaScript)
packages/form-core/src/FieldApi.ts (116:35)
114:             : undefined
115: 
116:           if (state.value !== this.#prevState.value) {
                                        ^
117:             this.validate('change', state.value)
118:           }
Error: Private field '#prevState' must be declared in an enclosing class (Note that you need plugins to import files that are not JavaScript)
    at error (/home/runner/work/form/form/node_modules/.pnpm/rollup@2.[78](https://github.com/TanStack/form/actions/runs/5260366012/jobs/9507176611?pr=399#step:6:79).1/node_modules/rollup/dist/shared/rollup.js:198:30)
    at Module.error (/home/runner/work/form/form/node_modules/.pnpm/[email protected]/node_modules/rollup/dist/shared/rollup.js:12560:16)
    at Module.tryParse (/home/runner/work/form/form/node_modules/.pnpm/[email protected]/node_modules/rollup/dist/shared/rollup.js:12937:25)
    at Module.setSource (/home/runner/work/form/form/node_modules/.pnpm/[email protected]/node_modules/rollup/dist/shared/rollup.js:12[84](https://github.com/TanStack/form/actions/runs/5260366012/jobs/9507176611?pr=399#step:6:85)2:24)
    at ModuleLoader.addModuleSource (/home/runner/work/form/form/node_modules/.pnpm/[email protected]/node_modules/rollup/dist/shared/rollup.js:22284:20)

[codesandbox-ci]

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