[BUG] tldr should fallback to other operating systems if the article is not available for the current OS

[5HT2]

Is there an existing issue for this?

• I have searched the existing issues

Current Behavior

Expected Behavior

I would expect tldr++ to fallback to the Linux version while on macOS, if the article only exists for Linux.

This is the behavior that other implementations of tldr use.

Steps To Reproduce

1. Try tldr efibootmgr on macOS
2. Try TLDR_OS=linux tldr efibootmgr

Environment

- OS:
`macOS 14.6.1`

- Terminal emulator:
`iTerm2 3.5.11`

- Go version:
`go version go1.23.3 darwin/arm64`

Anything else?

No response