[Meta] Prepare 8.x-1.4 release

Prepare 8.x-1.4 release by

1. Review open issues and identify them to include in 8.x-1.4 release
2. Add release notes and create release.

Possible 8.x-1.4 issues

See issue queue, all are possible at this time.

• #3024782: Install file incorrectly named
• #3011858: AdminSettingsForm fields not required, default values and code styling
• #2895595: $this->t() should be used instead of t() for Drupal 8 version.
• #3011872: PriceSpiderService getting country code from language doesn't work
• #3012143: JS Library doesn't properly define the async attribute
• #3018878: PriceSpider doesn't rebind on async renders

Follow-Up Steps

Here are some notes taken while reviewing the open 8.x issues. These may need new issues created as follow up tasks.

• #3011858: AdminSettingsForm fields not required, default values and code styling - Why $form['metatags']['ps_account'] and $form['metatags']['ps_config'] were required, but not in documentation. Why are they needed at all?
• #3011872: PriceSpiderService getting country code from language doesn't work - Provide a messaging and/or validation of site's default country is not configured, or fallback country config option via price spider configuration.