[Meta] Add pages about resources & resource detection to concept & languages

[svrnm]

Add a new page to “concepts“ that talks about resources & detection in a general way

If available&applicable, add a page about resources & resource detection for each language, similar to this one:

• What resources are detected automatically?
• Adding resources via OTEL_RESOURCE_ATTRIBUTES
• Adding resources in code
• Adding a (non default) resource detector (e.g. container)

TODO:

• Concept
• C++
• .NET
• Erlang/Elixir
• Go
• Java
• JavaScript
• PHP
• Python
• Ruby
• Rust
• Swift

Note, I added all languages to get started, if this is not applicable for some of them, we can remove them.

[svrnm]

Added also that we need a page that talks about the concept of resources and how they are detected

[theletterf]

Wonder if we could pin this one and simlar, @svrnm

[svrnm]

Wonder if we could pin this one and simlar, @svrnm

I list them here: #3686, but we can also pin some of them directly