Add MCMCChainsExt to docs build (#822)

Author: penelopeysm

docs/make.jl

@@ -22,7 +22,7 @@ makedocs(;
     # The API index.html page is fairly large, and violates the default HTML page size
     # threshold of 200KiB, so we double that.
     format=Documenter.HTML(; size_threshold=2^10 * 400),
-    modules=[DynamicPPL],
+    modules=[DynamicPPL, Base.get_extension(DynamicPPL, :DynamicPPLMCMCChainsExt)],
     pages=[
         "Home" => "index.md", "API" => "api.md", "Internals" => ["internals/varinfo.md"]
     ],

docs/src/api.md

@@ -108,14 +108,14 @@ unfix
 
 DynamicPPL provides functionality for generating samples from the posterior predictive distribution through the `predict` function. This allows you to use posterior parameter samples to generate predictions for unobserved data points.
 
-```@docs
-predict
-```
-
 The `predict` function has two main methods:
 
  1. For `AbstractVector{<:AbstractVarInfo}` - useful when you have a collection of `VarInfo` objects representing posterior samples.
- 2. For `MCMCChains.Chains` - useful when you have posterior samples in the form of a `Chains` object from MCMCChains.jl.
+ 2. For `MCMCChains.Chains` (only available when `MCMCChains.jl` is loaded) - useful when you have posterior samples in the form of an `MCMCChains.Chains` object.
+
+```@docs
+predict
+```
 
 ### Basic Usage