Revise README for QuantumCollocation.jl migration (#244)

Updated README to reflect migration of QuantumCollocation.jl into Piccolo.jl meta-package.

Author: jack-champagne

README.md

@@ -1,3 +1,13 @@
+# PLEASE READ
+
+> [!WARNING]  
+> QuantumCollocation.jl is no-longer a standalone package in the Piccolo.jl ecosystem.
+> This package has been migrated into the Piccolo.jl meta-package, which is now monolithic
+> and contains QuantumCollocation.jl, PiccoloPlots.jl, and PiccoloQuantumObjects.jl. This
+> migration happened as of version [v1.0.0](https://github.com/harmoniqs/Piccolo.jl/releases/tag/v1.0.0) of Piccolo.jl
+> All future development will take place in [Piccolo.jl](https://github.com/harmoniqs/Piccolo.jl), please make issues
+> and pull requests there!
+
 <!--```@raw html-->
 <div align="center">
   <a href="https://github.com/harmoniqs/Piccolo.jl">
@@ -124,4 +134,4 @@ julia --project=docs
 > using LiveServer, Piccolo, Revise
 > servedocs(literate_dir="docs/literate")
 ```
-it will not build and serve.
+it will not build and serve.