DOC: fix a few outdated/broken links

Author: mgeier

doc/code-cells.ipynb

@@ -152,7 +152,7 @@
    "source": [
     "## Special Display Formats\n",
     "\n",
-    "See [IPython example notebook](https://nbviewer.jupyter.org/github/ipython/ipython/blob/main/examples/IPython Kernel/Rich Output.ipynb)."
+    "See [IPython example notebook](https://nbviewer.org/github/ipython/ipython/blob/main/examples/IPython%20Kernel/Rich%20Output.ipynb)."
    ]
   },
   {
@@ -322,7 +322,7 @@
     "symbolic links can be created in each directory.\n",
     "\n",
     "For more details, see\n",
-    "[Default Values for Matplotlib's \"inline\" Backend](https://nbviewer.jupyter.org/github/mgeier/python-audio/blob/master/plotting/matplotlib-inline-defaults.ipynb)."
+    "[Default Values for Matplotlib's \"inline\" Backend](https://nbviewer.org/github/mgeier/python-audio/blob/master/plotting/matplotlib-inline-defaults.ipynb)."
    ]
   },
   {

doc/links.ipynb

@@ -131,7 +131,7 @@
     "\n",
     "Create interactive webpages from Jupyter Notebooks\n",
     "\n",
-    "https://www.nbinteract.com/\n",
+    "https://www.samlau.me/nbinteract/\n",
     "\n",
     "https://github.com/SamLau95/nbinteract"
    ]

doc/markdown-cells.ipynb

@@ -117,8 +117,8 @@
     "but you can install a notebook extension in order to enable equation numbering:\n",
     "https://jupyter-contrib-nbextensions.readthedocs.io/en/latest/nbextensions/equation-numbering/readme.html.\n",
     "\n",
-    "Automatic Equation Numbering is enabled on https://nbviewer.jupyter.org/,\n",
-    "see e.g. the latest version of this very notebook at the link https://nbviewer.jupyter.org/github/spatialaudio/nbsphinx/blob/master/doc/markdown-cells.ipynb#Automatic-Equation-Numbering.\n",
+    "Automatic Equation Numbering is enabled on https://nbviewer.org/,\n",
+    "see e.g. the latest version of this very notebook at the link https://nbviewer.org/github/spatialaudio/nbsphinx/blob/master/doc/markdown-cells.ipynb#Automatic-Equation-Numbering.\n",
     "\n",
     "When using `nbsphinx`, you can use the following `mathjax3_config` setting in your `conf.py` file\n",
     "to enable automatic equation numbering in HTML output.\n",
@@ -492,7 +492,7 @@
     "\n",
     "While this works nicely with `nbsphinx`, JupyterLab and the Classic Jupyter Notebook,\n",
     "This doesn't work correctly in `nbconvert`\n",
-    "and by extension on https://nbviewer.jupyter.org/ and Github's notebook preview.\n",
+    "and by extension on https://nbviewer.org/ and Github's notebook preview.\n",
     "\n",
     "See https://github.com/jupyter/nbconvert/issues/1125.\n",
     "\n",