Use em-dash separator

Author: ehuss

src/attributes/debugger.md

@@ -150,9 +150,9 @@ The attribute uses the [_MetaListIdents_] syntax to specify its inputs, and can
 macro definitions.
 
 Accepted options:
-- `#[collapse_debuginfo(yes)]` - code locations in debuginfo are collapsed.
-- `#[collapse_debuginfo(no)]` - code locations in debuginfo are not collapsed.
-- `#[collapse_debuginfo(external)]` - code locations in debuginfo are collapsed only if the macro
+- `#[collapse_debuginfo(yes)]` — code locations in debuginfo are collapsed.
+- `#[collapse_debuginfo(no)]` — code locations in debuginfo are not collapsed.
+- `#[collapse_debuginfo(external)]` — code locations in debuginfo are collapsed only if the macro
   comes from a different crate.
 
 The `external` behavior is the default for macros that don't have this attribute, unless they are