Create a solution with lerna and 3 projects inside:

-Prerequisites:

Lerna and stencil must be installed in global

npm install --g lerna

1. Create lerna project

mkdir web-components
cd web-components
npx lerna init

2. Create a javascript library called "components-ui" with stencil

cd packages
npm init stencil

choose component enter a name for library : components-ui

cd components-ui
yarn add @stencil/core@latest --save-exact
yarn add @stencil/sass --dev
yarn add classnames
yarn add @types/classnames

Modify stencil.config.ts for adding plugin sass

Create your component (in my sample, it's a button) and modify index.html for showing the new component

Launch the application with

yarn run start

Build the components library and create a link

yarn run build
yarn link

3. Create a react application called "react-app"

cd packages
npx create-react-app react-app

Link the library with application

cd react-app
yarn link "components-ui"

Modify index.js and app.js for adding the component and start the app

yarn run start

4. Create a angular application called "angular-app"

cd packages
ng new angular-app

Link the library with application

cd angular-app
yarn link "components-ui"

Modify main.ts, app.component.html and app.component.ts for adding the component

Modify app.module.ts for adding CUSTOM_ELEMENTS_SCHEMA and start the app

yarn run start

Now you have a components library compatible with react and angular application (and more...)