add Eslint action and update travis CI (#931)

* refactor: eliminate eslint errors as many as I can

* refactor: fix more eslint errors in the record module

* LINT: fix @typescript-eslint/unbound-method

* LINT: fix all eslint errors in source code

* LINT: fix as many eslint warnings as possible

* CI: add a github action to check ESLINT status

* CI: update github action

* build: update travis CI and github action

* CI: update github action

* CI: update job name

* CI: restore test command from turbo to lerna

* Merge branch master into eslint-action

Co-authored-by: Justin Halsall <Juice10@users.noreply.github.com>

package.json

@@ -36,7 +36,8 @@
     "test:watch": "yarn turbo run test:watch",
     "dev": "yarn turbo run dev",
     "repl": "cd packages/rrweb && npm run repl",
-    "lint": "yarn run concurrently --success=all -r -m=1 'yarn run markdownlint docs' 'yarn eslint packages/*/src --ext .ts,.tsx,.js,.jsx,.svelte'"
+    "lint": "yarn run concurrently --success=all -r -m=1 'yarn run markdownlint docs' 'yarn eslint packages/*/src --ext .ts,.tsx,.js,.jsx,.svelte'",
+    "lint:report": "yarn eslint --output-file eslint_report.json --format json packages/*/src --ext .ts,.tsx,.js,.jsx"
   },
   "resolutions": {
     "**/jsdom/cssom": "https://registry.npmjs.org/rrweb-cssom/-/rrweb-cssom-0.6.0.tgz"