[WIP] Floating Point Article

[apopiak]

This is a WIP PR for adding a floating point article to the knowledge base. Why they are a bad idea in a runtime etc.

Thank you for making a PR to the knowledge base. Please make sure it follows these short guidelines:

• Are the audience and objective of the document clear?
• Is the writing:
  • Clear: All jargon defined, explained, or linked to. Best to avoid it.
  • Precise: No ambiguous meanings
  • Concise: Free of superfluous detail
• Does it follow our style guide?
• If this is a new page, does the PR include the appropriate infrastructure, e.g. adding the
  page to a sidebar?
• Build the page. Does it render properly? E.g. no funny lists or formatting.
• Links should go to rustdocs or devhub articles, not source code.
• If this PR addresses an issue in the queue, have you referenced it in the description?