[CHORE]: Change default to `true` for `responsive` config attribute

[camdecoster]

Description

Change default to true for the responsive config attribute.

Why should this change be made?

We said we would do it in v3, but we forgot 🤷. It's arguably a better experience for users.

Scope

• Change the default in this section:
  

  plotly.js/src/plot_api/plot_config.js

  Lines 127 to 133 in 174319a

  	responsive: {
  	valType: 'boolean',
  	dflt: false,
  	description: [
  	'Determines whether to change the layout size when window is resized.',
  	'In v3, this option will be removed and will always be true.'
  	].join(' ')

Notes

• Before flipping this switch, run through the backlog and check for any issues that should be addressed first