* feat(reactivity): `proxyRefs` method and `ShallowUnwrapRefs` type
BREAKING CHANGE: template auto ref unwrapping are now applied shallowly,
i.e. only at the root level. See https://github.com/vuejs/vue-next/pull/1682 for
more details.
- v-model and v-show directives are now exposed as public
- compiler-used runtime helpers are now exposed for TS tooling, but marked as @private
close#1329
Packages can now augment the ref unwrap bail types in their own `d.ts`.
Also updated the build script to auto concat any files in a package's
`types` directory to the final generated `d.ts`.
- `@vue/reactivity` should no longer require `libs: ["DOM"]` in tsconfig
- Properly bail on `VNode` and `ComponentPublicInstance` in runtime-core
BREAKING CHANGE: Reactivity APIs adjustments:
- `readonly` is now non-tracking if called on plain objects.
`lock` and `unlock` have been removed. A `readonly` proxy can no
longer be directly mutated. However, it can still wrap an already
reactive object and track changes to the source reactive object.
- `isReactive` now only returns true for proxies created by `reactive`,
or a `readonly` proxy that wraps a `reactive` proxy.
- A new utility `isProxy` is introduced, which returns true for both
reactive or readonly proxies.
- `markNonReactive` has been renamed to `markRaw`.
BREAKING CHANGE: `<portal>` has been renamed to `<teleport>`.
`target` prop is also renmaed to `to`, so the new usage will be:
```html
<Teleport to="#modal-layer" :disabled="isMobile">
<div class="modal">
hello
</div>
</Teleport>
```
The primary reason for the renaming is to avoid potential naming
conflict with [native portals](https://wicg.github.io/portals/).
Note the behavior is different from Vue 2:
- merge strategies no longer apply to built-in options.
- the default value is now an empty object and no longer exposes merge
strategies for built-in options.
BREAKING CHANGE: replae `watch(fn, options?)` with `watchEffect`
The `watch(fn, options?)` signature has been replaced by the new
`watchEffect` API, which has the same usage and behavior. `watch`
now only supports the `watch(source, cb, options?)` signautre.
