Integrate gatsby-plugin-intl for internationalization
Replaces static text with `intl.formatMessage` call and Links with `gatsby-plugin-intl` equivalent
Note: `npm install` now requires `--force` to install the latest `gatsby-plugin-intl` as it doesn't explicitly support gatsby3.0
* Addresses issue #16 -
Add styles via sass and module imports
Adds typed scss imports via gatsby-plugin-sass.
Makes use of .d.scss file generated by gatsby-plugin-scss-typescript,
but avoids importing that directly while they work out issue in gatsby v3.
* adding vscode config for easier local debugging
