Extract form to a separate package & use new export features (#77)

* refactor(frontend): use new export features for packages

* refactor(frontend): extract form to a separate package

* refactor(frontend): add gitignore to ignore built files

* fix(frontend): address building issues

* fix(frontend): address "address already in use" error

* refactor(frontend): address review commits

* chore(frontend): add README.md

README.md

@@ -9,3 +9,9 @@ Vaadin Fusion
 Join the Vaadin Fusion community chat in https://vaad.in/fusion
 
 **Note**: Currently the code of Vaadin Fusion is hosted at https://github.com/vaadin/flow together with the Flow framework. The Fusion-only code will be ported to this repository in the near future. Tickets can already be created in this repository.
+
+## Packages
+
+| Package                        |
+|--------------------------------|
+| [@vaadin/frontend](./frontend) |

frontend/.gitignore

@@ -0,0 +1,4 @@
+packages/*/*.d.ts
+packages/*/*.d.ts.map
+packages/*/*.js
+packages/*/*.js.map

frontend/README.md

@@ -0,0 +1,29 @@
+# Vaadin Frontend
+
+The collection of frontend utilities used by Vaadin Flow and Fusion.
+
+| Package                 | Status |
+|-------------------------|--------|
+| [@vaadin/common-frontend](./packages/common-frontend) | [![Latest Stable Version](https://img.shields.io/npm/v/@vaadin/common-frontend.svg)](https://www.npmjs.com/package/@vaadin/common-frontend) |
+| [@vaadin/fusion-frontend](./packages/fusion-frontend) | [![Latest Stable Version](https://img.shields.io/npm/v/@vaadin/fusion-frontend.svg)](https://www.npmjs.com/package/@vaadin/fusion-frontend) |
+
+## Contribution
+
+You can download the project and run tests using the following commands:
+```bash
+$ git clone https://github.com/vaadin/fusion.git
+$ cd fusion
+$ npm install
+$ npm run build
+$ npm test
+```
+
+## Requirements
+
+To work with this project as a developer, you need the following versions of `node` and `npm`:
+
+- **NodeJS**: `^12.20.0 || ^14.13.1 || >=16.0.0` (native support for ES Modules),
+- **npm**: `^7` (`package-lock.json` is of version 2; also, `lerna` is unable to bootstrap this project correctly with lower `npm`)
+
+
+