Use govuk_elements as a Node.js dependency

[RobinKnipe]

Added a version number to `package.json'.

Allows the project to be installed as a dependency with NPM.

Tested by inclusion into another project.
This project can now be added as a dependency in any Node.js project as described in the following steps:

• install the dependency

npm install --save alphagov/govuk_elements

• require the code

require('govuk-elements/assets/javascripts/govuk/details.polyfill');

About the change:

• New feature (non-breaking change which adds functionality)

• My change requires a change to the documentation.

• I have updated the documentation accordingly.

• I have read the CONTRIBUTING document.

[gemmaleigh]

Hi @RobinKnipe,

Thanks for this. If you'd like to use GOV.UK elements - the sass files are available as an NPM package.

https://github.com/alphagov/govuk_elements/tree/master/packages/govuk-elements-sass

The govuk_elements application isn't intended to be included as a dependency in this way, that's why the package.json file in the root isn't versioned.

I'm not sure it's a good idea to require the entire app as a dependency to include a single file.

I'll raise an issue to move the details polyfill to the govuk_frontend_toolkit, where the rest of our shared JavaScript lives.

[gemmaleigh]

We have an issue already: #400.

Sorry there hasn't been any movement on it, will try to prioritise it!

[RobinKnipe]

Hi @gemmaleigh - thanks for getting back to me. I'm happy to get the polyfill from the govuk_frontend_toolkit if that's easier. I'll close this PR...