Fix Jupyter Lite serve instruction

Author: mcbarton

CONTRIBUTING.md

@@ -161,5 +161,7 @@ jupyter lite build --XeusAddon.prefix=$PREFIX \
 
 Once the Jupyter Lite site has built you can test the website locally by executing
 ```bash
-jupyter lite serve --XeusAddon.prefix=$PREFIX
+jupyter lite serve --XeusAddon.prefix=$PREFIX \
+                   --XeusAddon.mounts="$PREFIX/share/xeus-cpp/tagfiles:/share/xeus-cpp/tagfiles" \
+                   --XeusAddon.mounts="$PREFIX/etc/xeus-cpp/tags.d:/etc/xeus-cpp/tags.d" 
 ```

README.md

@@ -173,7 +173,9 @@ jupyter lite build --XeusAddon.prefix=$PREFIX \
 
 Once the Jupyter Lite site has built you can test the website locally by executing
 ```bash
-jupyter lite serve --XeusAddon.prefix=$PREFIX
+jupyter lite serve --XeusAddon.prefix=$PREFIX \
+                   --XeusAddon.mounts="$PREFIX/share/xeus-cpp/tagfiles:/share/xeus-cpp/tagfiles" \
+                   --XeusAddon.mounts="$PREFIX/etc/xeus-cpp/tags.d:/etc/xeus-cpp/tags.d" 
 ```
 
 ## Trying it online

docs/source/InstallationAndUsage.rst

@@ -145,7 +145,9 @@ Once the Jupyter Lite site has built you can test the website locally by executi
 
 .. code-block:: bash
 
-    jupyter lite serve --XeusAddon.prefix=$PREFIX
+    jupyter lite serve --XeusAddon.prefix=$PREFIX \
+                       --XeusAddon.mounts="$PREFIX/share/xeus-cpp/tagfiles:/share/xeus-cpp/tagfiles" \
+                       --XeusAddon.mounts="$PREFIX/etc/xeus-cpp/tags.d:/etc/xeus-cpp/tags.d" 
 
 Installing from conda-forge
 ===========================