Allow snapshot strategy to be configured

We want people to be able to use the new "clip" snapshot strategy that
happo-e2e has made available.

The clip strategy means the whole dom is included in the snapshot, and
happo workers will clip the screenshot based on where the
`[data-happo-clip]` element is located.

cypress/integration/home_page_spec.js

@@ -41,6 +41,12 @@ describe('The Home Page', () => {
       component: 'Card',
       log: false,
     });
+    cy.get('.card', { log: false }).happoScreenshot({
+      component: 'Card',
+      variant: 'snapshotStrategy clip',
+      log: false,
+      snapshotStrategy: 'clip',
+    });
     cy.get('.card,.button', { log: false }).happoScreenshot({
       includeAllElements: true,
       component: 'Card + Button',

index.js

@@ -50,6 +50,7 @@ Cypress.Commands.add(
       includeAllElements,
       transformDOM,
       targets,
+      snapshotStrategy = 'hoist',
       ...otherOptions
     } = options;
 
@@ -75,6 +76,7 @@ Cypress.Commands.add(
       element: includeAllElements ? originalSubject : originalSubject[0],
       responsiveInlinedCanvases: resInCan,
       transformDOM: transformDOM,
+      strategy: snapshotStrategy,
       handleBase64Image: ({ src, base64Url }) => {
         const rawBase64 = base64Url.replace(/^data:image\/png;base64,/, '');
         const chunks = chunked(rawBase64, config.canvasChunkSize);