Assorted TODO

[XhmikosR]

Here's a few things I'd personally like fixed (the order might matter for some things):

• Make it clear which Node.js versions are supported. CI fails for Node.js 6, but it seems it's a devDependency issue. Either way, we need to clear this up and make sure whatever CI we use runs on all supported Node.js versions
• We need lock files for both core and store
• We need to enable security alerts in the repo settings
• We need dependabot enabled for security issues on the repo in https://github.com/siddharthkp/bundlesize/network/alerts
• We need to remove the unused/old greenkeeper branches from the repo
• We need to enable "Automatically delete head branches" repo option
• Enforce 2fa for all people with push rights on the repo
• Enforce 2fa on npm too for people with push rights
• Revisit third-party hooks and integrations and remove any unused ones
• Register for GitHub Actions - draft PR Switch to GitHub Actions CI. #336