docs: use sphinx var for min node version

docs/source/conf.py

@@ -70,6 +70,7 @@ myst_enable_extensions = [
 myst_substitutions = {
     # date example: Dev 07, 2022
     "date": datetime.date.today().strftime("%b %d, %Y").title(),
+    "node_min": "12",
     "python_min": "3.8",
     "version": jupyterhub.__version__,
 }

docs/source/contributing/setup.md

@@ -18,7 +18,7 @@ installed Python before, the recommended way to install it is to use
 
 ### Install nodejs
 
-[NodeJS 12+](https://nodejs.org/en/) is required for building some JavaScript components.
+[NodeJS {{node_min}}+](https://nodejs.org/en/) is required for building some JavaScript components.
 `configurable-http-proxy`, the default proxy implementation for JupyterHub, is written in Javascript.
 If you have not installed NodeJS before, we recommend installing it in the `miniconda` environment you set up for Python.
 You can do so with `conda install nodejs`.

docs/source/tutorial/quickstart.md

@@ -9,7 +9,7 @@ Before installing JupyterHub, you will need:
   of using [`pip`](https://pip.pypa.io) or
   [`conda`](https://docs.conda.io/projects/conda/en/latest/user-guide/getting-started.html) for
   installing Python packages is helpful.
-- [nodejs/npm](https://www.npmjs.com/). [Install nodejs/npm](https://docs.npmjs.com/getting-started/installing-node),
+- [Node.js {{node_min}}](https://www.npmjs.com/) or greater, along with npm. [Install Node.js/npm](https://docs.npmjs.com/getting-started/installing-node),
   using your operating system's package manager.
 
   - If you are using **`conda`**, the nodejs and npm dependencies will be installed for
@@ -24,7 +24,7 @@ Before installing JupyterHub, you will need:
     ```
 
     [nodesource][] is a great resource to get more recent versions of the nodejs runtime,
-    if your system package manager only has an old version of Node.js (e.g. 10 or older).
+    if your system package manager only has an old version of Node.js.
 
 - A [pluggable authentication module (PAM)](https://en.wikipedia.org/wiki/Pluggable_authentication_module)
   to use the [default Authenticator](authenticators).