Clarify in documentation that "#" is or is not a valid "inline comment" token

[HCL specs](https://github.com/hashicorp/hcl/blob/main/hclsyntax/spec.md) indicate `#` is a "line comment" and declares that only the `/* */` syntax meets the categorization of an "inline comment"

This is counter-intuitive to how most HCL-based tools actually interpret a `#` comment when used _inline_ after valid code. Most tools, including Terraform, view a `#` comment inline after other valid HCL statements to be treated as a valid inline comment (and it is ignored accordingly)

Read hclsyntax/spec.md, especially its definitions of line and inline comments, then compare those statements with the inline `#` behavior described in the issue. Update the documentation so the status of `#` as an inline comment is unambiguous and consistent with the stated behavior.

Written by the indexing model from the issue text.