Variety of updates to modernize coverage of strict mode

[getify]

Summary

Removed a lot of old/incorrect or misleading information, including links to blog posts that are over a decade old and don't offer accurate information on the topic. Also clarified how Appendix B modifies some of strict mode's behaviors for browser JS environments (including the engine in Node.js).

Motivation

This text was really out of date. It doesn't seem to have been touched since ES6 (2015), and was still laden by a lot of outdated (and in some cases, inaccurate) information about strict mode from ES5 back around 2011.

Supporting details

• https://tc39.es/ecma262/#sec-additional-ecmascript-features-for-web-browsers
• https://caniuse.com/use-strict

Related issues

n/a

Metadata

• Adds a new document
• Rewrites (or significantly expands) a document
• Fixes a typo, bug, or other error

[github-actions]

Preview URLs

• https://pr14186.content.dev.mdn.mozit.cloud/en-US/docs/Web/JavaScript/Reference/Strict_mode

Flaws

None! 🎉

External URLs

URL: /en-US/docs/Web/JavaScript/Reference/Strict_mode
Title: Strict mode
on GitHub

• https://caniuse.com/use-strict (1 time) (Note! This may be a new URL 👀)
• https://tc39.es/ecma262/ (3 times) (Note! This may be a new URL 👀)

[wbamberg]

👍 thank you @getify , great update!