fix typo in button locator and update test

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- added missing `#` in `"#btn-become-supporter"`
- updated test on Landing Page to check this button (was missing)
- ran Playwright test to confirm passed

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frontend/tests/page-objects/LandingPage.ts

@@ -10,7 +10,7 @@ export default class LandingPage extends BasePage {
     GET_ORGANIZED_BUTTON: "#btn-get-organized",
     GROW_ORGANIZATION_BUTTON: "#btn-grow-organization",
     ABOUT_BUTTON: "#btn-activist",
-    BECOME_SUPPORTER_BUTTON: "btn-become-supporter",
+    BECOME_SUPPORTER_BUTTON: "#btn-become-supporter",
     OUR_SUPPORTERS_BUTTON: "#btn-our-supporters",
   };
 

frontend/tests/specs/landing-page.spec.ts

@@ -136,6 +136,7 @@ test.describe("Landing Page", () => {
     await expect(landingPage.getOrganizedButton).toBeVisible();
     await expect(landingPage.growOrganizationButton).toBeVisible();
     await expect(landingPage.aboutButton).toBeVisible();
+    await expect(landingPage.becomeSupportersButton).toBeVisible();
     await expect(landingPage.ourSupportersButton).toBeVisible();
   });
 });