add information about help mode for variables with metadata

Author: baggepinnen

docs/src/basics/Variable_metadata.md

@@ -1,6 +1,7 @@
 # Symbolic metadata
-It is possible to add metadata to symbolic variables. The following
-information can be added (note, it's possible to extend this to user-defined metadata as well)
+It is possible to add metadata to symbolic variables, the metadata will be displayed when calling help on a variable.
+
+The following information can be added (note, it's possible to extend this to user-defined metadata as well)
 
 ## Variable descriptions
 Descriptive strings can be attached to variables using the `[description = "descriptive string"]` syntax:
@@ -19,6 +20,20 @@ When variables with descriptions are present in systems, they will be printed wh
 show(stdout, "text/plain", sys) # hide
 ```
 
+Calling help on the variable `u` displays the description, alongside other metadata:
+```julia
+help?> u
+
+  A variable of type Symbolics.Num (Num wraps anything in a type that is a subtype of Real)
+
+  Metadata
+  ≡≡≡≡≡≡≡≡≡≡
+
+  ModelingToolkit.VariableDescription: This is my input
+
+  Symbolics.VariableSource: (:variables, :u)
+```
+
 ## Input or output
 Designate a variable as either an input or an output using the following
 ```@example metadata

src/variables.jl

@@ -286,7 +286,3 @@ end
 function hasdescription(x)
     getdescription(x) != ""
 end
-
-function Base.Docs.getdoc(p::Num)
-    string(Base.Docs.@doc(p), " ", getdescription(p))
-end