docs: Updated images.md to describe how to include local images to your build.

[martijnvanschie]

Added notes on how to include additional local resources (like images) to your build so that are available in the deployed app.

PR Checklist

• [x] The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/CONTRIBUTING.md#commit-messages.
• [x] If there is an issue related with this PR, point it out here.

What is the current state of the documentation article?

Additinal configuration to get local images to work. Could not find this and finally got answer using slack community.

What is the new state of the documentation article?

Added new sections.

Fixes/Implements/Closes #[Issue Number].

[cla-bot[bot]]

Thank you for your pull request and welcome to our community. We require contributors to sign our Contributor License Agreement, and we don't seem to have you on file. In order for us to review and merge your code, please sign the CLA at https://www.nativescript.org/cla. CLA has not been signed by users: @martijnvanschie. After signing the CLA, you can ask me to recheck this PR by posting @cla-bot check as a comment to the PR.

[martijnvanschie]

@cla-bot check

[cla-bot[bot]]

The cla-bot has been summoned, and re-checked this pull request!