feat: Add lockfile and locking script

* Move environment definition file to top level directory.
* Add conda-lock lock script that uses Docker and conda-lock to
  build a conda-lock lock file and then move it to binder/environment.yml
  to serve as the conda config file for Binder.
* Add built lock file.

Author: matthewfeickert

README.md

@@ -12,7 +12,7 @@ Talk on pyhf new features at the PyHEP 2023 workshop
 ### conda/mamba/micromamba
 
 ```
-micromamba env create --file binder/environment.yml
+micromamba env create --file environment.yml
 ```
 
 and then activate the environment