Move docs deployment from Travis CI to GitHub Actions

[tlylt]

What is the purpose of this pull request?

• Documentation update
• Bug fix
• Feature addition or enhancement
• Code maintenance
• Others, please explain:
  DevOps

Overview of changes:
Fixes #1386

• Delete Travis CI config file
  • Might need one of the senior devs to disable build settings on Travis (not sure)
• Update GitHub Actions workflow to deploy docs
  • (same as previous flow)
  • deploy DG on every commit to master
  • deploy UG on release, this is done when the tag of the new version is pushed
• Consolidate some build/deploy commands into package.json
• Update devGuide to use the new npm run build:ug etc commands

Anything you'd like to highlight / discuss:
Not able to test this locally, but I have created a sample repo to test the CI logic, which seems to be correct. Some intended runs as follows:

• For PR against master, only run test: https://github.com/tlylt/gh-workflow-example/pull/4
• For PR merged to master, only run test + deploy dg: https://github.com/tlylt/gh-workflow-example/runs/5154822398?check_suite_focus=true
• For pushing a tag (something that is done just before release), run test + deploy dg + deploy ug: https://github.com/tlylt/gh-workflow-example/runs/5153160394?check_suite_focus=true

Testing instructions:
See above. Reference: Workflow syntax

Proposed commit message: (wrap lines at 72 characters)
Move docs deployment from Travis CI to GitHub Actions

There is a change to Travis' pricing model.

Let's move docs deployment into GitHub Actions and remove
the usage of Travis from our CI processes.

This will potentially remove any costs incurred when using Travis.

---

Checklist: ☑️

• Updated the documentation for feature additions and enhancements
• Added tests for bug fixes or features
• Linked all related issues
• No unrelated changes

[ong6]

Nice work! The changes so far look good! I don't think this exactly fixes the issue of #1386 but will certainly help reduce the build minutes with Travis. I think I'll leave it to one of the senior dev's to approve this PR instead.

approved wronly

[jonahtanjz]

Great job @tlylt 👍 Just a minor suggestion, other than that the rest looks good :)

Might need one of the senior devs to disable build settings on Travis (not sure)

Yup will need @ang-zeyu help to turn off Travis integration.

[jonahtanjz]

Thanks @tlylt

One last thing, I noticed that our README file still has the build status badge pointing to Travis. Will need to update this as well :)

[tlylt]

Thanks @tlylt

One last thing, I noticed that our README file still has the build status badge pointing to Travis. Will need to update this as well :)

Yup sorry forgot about it, will change accordingly.

[jonahtanjz]

LGTM 👍