[toml/en] Update and add contents following TOML v1.0.0 spec

[GymRat102]

When I was doing the translation of TOML docs into zh-cn, I've noticed that the content has been somewhat outdated or confused for learners. I checked the git history and found that the original content was written mainly under TOML spec v0.4.0. Even though later contributor changed doc and declared it follows spec v1.0.0, I've tracked back to old spec and noticed that some parts of this page still follow old example or explanation.

Therefore, I updated and add contents into this doc according to current spec. The result is that I deleted some of the irrelevant or outdated content, and add important contents after skimming through TOML spec, both in my opinion. I'd love to explain and discuss the changes, and modify if necessary.
 

• I solemnly swear that this is all original content of which I am the original author
• Pull request title is prepended with [language/lang-code] (example [python/fr-fr] or [java/en])
• Pull request touches only one file (or a set of logically related files with similar changes made)
• Content changes are aimed at intermediate to experienced programmers (this is a poor format for explaining fundamental programming concepts)
• If you've changed any part of the YAML Frontmatter, make sure it is formatted according to CONTRIBUTING.md
  • Yes, I have double-checked quotes and field names!