Prettier plugin settings

[mattpass]

Consider non default settings for Prettier and if we should apply any user defined settings such as number of space chars for indents.

[mattpass]

Also, checkboxes for:

• Format on save (on by default)
• Format on paste
• Format on type

[mattpass]

Prettier is by it's nature not really supposed to be configurable as it has a set of best practice rules enforced. However, we should respect 2 items as per the users choice - indent type and size.

See here for config flags for those:
https://prettier.io/docs/en/options.html

[mattpass]

Added those 2 config options to JSON passed to Prettier in 7904886.

As for settings more generally, issues have been raised to cover this.