Document migration of 0.1.1 to 0.2.0

[sverhoeven]

Due to Typescript and TSLint the migration is more complex than the description in the CHANGELOG.md.

Add steps to migrate in CHANGELOG.md

[sverhoeven]

In an app created with 0.1.1 ran:

npm install --save-dev --save-exact @nlesc/react-scripts@0.2.0
curl https://raw.githubusercontent.com/NLeSC/create-react-app/%40nlesc/react-scripts%400.2.0/packages/react-scripts/template/tsconfig.json > tsconfig.json
curl https://raw.githubusercontent.com/NLeSC/create-react-app/%40nlesc/react-scripts%400.2.0/packages/react-scripts/template/tslint.json > tslint.json

Ran npm run lint which gave bunch of errors. In VSCode applied auto fix to each file.
See 3D-e-Chem/molviewer-tsx@1b43005 for the required changes.