Package graduation

## Background

When we started this project, it was a single package (`frint`) in a single repository.

Earlier this year, we focused on the core `frint` package to handle Apps and dependency injection only (since v1), and split other stuff into separate packages, going ahead with a monorepo structure.

Some packages do share the prefix of `frint-` but have nothing to do with FrintJS directly. For e.g., `frint-store` and `frint-data` can live completely on their own.

While monorepo allowed us to build everything together nicely, the last 20-30 releases saw some packages upgrading to another minor/major version even when they didn't have any changes within them.

## Graduate some packages to their own repos

I suggest, export some packages into their own repos. I can think of creating two repos at the moment:

* `frint-store` repo: will contain `frint-store`
* `frint-data` repo: will contain `frint-data` and upcoming `frint-data-validation` packages

## Process

* Push the `frintjs/frint` repo to `frintjs/repo-name` first
* Remove everything else from `frintjs/repo-name` that is not specific to that package
* This way, we can maintain our contributions data from multiple authors

Review the monorepo package layout and the `frint-store` and `frint-data` package entry points first; no specific files or tests are identified in the issue. Define the repository split, including `frint-data-validation`, and confirm that each new repository retains the relevant package history and removes unrelated content.

Written by the indexing model from the issue text.