Add support for filters in webhook registration

[kennyadsl]

What this PR does

To support passing a filter to webhook registrations, the filter parameter is needed.

Depends on Shopify/shopify-api-ruby#1347

Reviewer's guide to testing

gem "shopify_api", github: 'nebulab/shopify-api-ruby', branch: 'kennyadsl/add-filter-support'
gem "shopify_app", github: 'nebulab/shopify_app', branch: 'kennyadsl/add-filter-support'

The following registration won't work without the changes in the two PRs above, because apparently, to register a metaobject-related webhook, at least one filter needs to be specified.

ShopifyApp.configure do |config|
  config.webhooks = [
    {
      topic: "metaobjects/update",
      path: "api/webhooks/metaobjects_update",
      filter: "type:my_type OR type:my_other_type",
    },
  ]
end

Checklist

Before submitting the PR, please consider if any of the following are needed:

• Update CHANGELOG.md if the changes would impact users
• Update README.md, if appropriate.
• Update any relevant pages in /docs, if necessary
• For security fixes, the Disclosure Policy must be followed.

[matteodepalo]

LGTM, thank you for your contribution!

[matteodepalo]

@kennyadsl could you update the shopify_api version to 14.7.0?

[kennyadsl]

@matteodepalo done!