Add tslint-playground to README and bug report template.

[johnwiseheart]

PR checklist

• Addresses an existing issue: Add tslint-playground link to README and other docs #4125
• New feature, bugfix, or enhancement
  • Includes tests
• Documentation update

Overview of change:

Add tslint-playground to README and bug report template.

Is there anything you'd like reviewers to focus on?

CHANGELOG.md entry:

[docs] Add tslint-playground to README and bug report template.

[JoshuaKGoldberg]

Note: I removed the extra "Creating a New Release" section.

Creating a new release

1. Bump the version number in package.json and src/linter.ts
2. Add release notes in CHANGELOG.md
   • Use ./scripts/generate-changelog.js (after building it with tsc -p scripts) to generate the changelog diff. This script expects > a Github.com personal access token to exist at ~/github_token.txt with "repo" permissions.
3. Commit with message Prepare release <version>
4. Push your branch to GitHub and make a PR
5. Once your PR is merged, wait for the tests to pass on CircleCI for develop
6. Create a "Release" on GitHub with the proper tag version and notes from the changelog.
   • The tag should be identical to the version in package.json
7. Run yarn run publish:local