Mention docstrings in the style guide (#57580)

Mention docstrings in the style guide and link to the section of the
manual that gives more detail.

Author: LilithHafner

doc/src/manual/documentation.md

@@ -23,7 +23,7 @@ environments provide a way to access documentation directly:
 `Docs.hasdoc(module, name)::Bool` tells whether a name has a docstring. `Docs.undocumented_names(module; all)`
 returns the undocumented names in a module.
 
-## Writing Documentation
+## [Writing Documentation](@id man-writing-documentation)
 
 Julia enables package developers and users to document functions, types and other objects easily
 via a built-in documentation system.

doc/src/manual/style-guide.md

@@ -19,6 +19,11 @@ Julia's compiler works.
 It is also worth emphasizing that functions should take arguments, instead of operating directly
 on global variables (aside from constants like [`pi`](@ref)).
 
+## Write docstrings
+
+Comments describing an object should typically be written as [docstrings](@ref man-writing-documentation) for editor and REPL accessibility.
+Inline comments (`# comment`) and multiline comments (`#= comment =#`) are appropriate for information that is intended only for the reader of the code (as opposed to a user).
+
 ## Avoid writing overly-specific types
 
 Code should be as generic as possible. Instead of writing: