Travis-CI documentation should be changed to Github Actions

[aguang]

As we are migrating from Travis-CI to Github Actions now, we should change all portions of the documentation that provide templates or references to Travis-CI. This includes:

• The reference to .travis.yml in the Home page
• The Travis-CI icon in the README template
• The section with Travis-CI code for the Documentation Set Up
• The section with Travis-CI code for the Semantic Release