Update CI badge to point to GitHub Actions

Summary:
I noticed both the image and the link of the build badge in our README was pointing to the previous CI service we were using, which has since shut down. 🫡

This diff updates the link and image to point to build progress screen for the CI script.

Reviewed By: DimaVartanian

Differential Revision: D42996404

fbshipit-source-id: b20464c744606392549a829849a7adddf032cb24

README.md

@@ -3,8 +3,8 @@
 </p>
 
 <p align="center">
-    <a href="https://travis-ci.org/Instagram/IGListKit">
-        <img src="https://travis-ci.org/Instagram/IGListKit.svg?branch=main&style=flat"
+    <a href="https://github.com/Instagram/IGListKit/actions/workflows/CI.yml">
+        <img src="https://img.shields.io/github/actions/workflow/status/Instagram/IGListKit/CI.yml"
              alt="Build Status">
     </a>
     <a href="https://coveralls.io/github/Instagram/IGListKit?branch=main">

README.zh.md

@@ -3,8 +3,8 @@
 </p>
 
 <p align="center">
-    <a href="https://travis-ci.org/Instagram/IGListKit">
-        <img src="https://travis-ci.org/Instagram/IGListKit.svg?branch=main&style=flat"
+    <a href="https://github.com/Instagram/IGListKit/actions/workflows/CI.yml">
+        <img src="https://img.shields.io/github/actions/workflow/status/Instagram/IGListKit/CI.yml"
              alt="Build Status">
     </a>
     <a href="https://coveralls.io/github/Instagram/IGListKit?branch=main">