Docs: Add release version pinning to conda install instructions (#4147)

Automatically adds the current release version to the conda install instructions.

Adding the version explicitly significantly improves the performance 
of the conda environment solver. It might be possible to remove the 
explicit version in the future pending improvements of the solver
 implementation.

docs/source/intro/get_started.rst

@@ -85,22 +85,22 @@ Install Software
 
     :fa:`download,mr-1` **Install from Conda**
 
-    .. code-block:: console
+    .. parsed-literal::
 
-        $ conda create -n aiida -c conda-forge aiida-core aiida-core.services
-        $ conda activate aiida
-        $ reentry scan
+        conda create -n aiida -c conda-forge aiida-core=\ |release|\  aiida-core.services=\ |release|
+        conda activate aiida
+        reentry scan
 
-    `Conda <https://docs.conda.io>`__ provides a cross-platform package management system, from which we can install all the basic components of the AiiDA infrastructure in an isolated environment:
+    `Conda <https://docs.conda.io>`__ provides a cross-platform package management system, from which we can install all the basic components of the AiiDA infrastructure in an isolated environment.
 
     ----------------------------------------------
 
     :fa:`download,mr-1` **Install with pip**
 
-    .. code-block:: console
+    .. parsed-literal::
 
-        $ pip install aiida-core
-        $ reentry scan
+        pip install aiida-core
+        reentry scan
 
     ``aiida-core`` can be installed from `PyPi <https://pypi.org/project/aiida-core>`__.
     It is strongly recommended that you install into a :ref:`virtual environment <intro:install:virtual_environments>`.