README: Update instructions to build the website

README

@@ -12,8 +12,8 @@ This website is developed using the [[https://guix.gnu.org/download/][GNU Guix]]
 Run the following command in the website folder (=cd path/to/website=):
 
 #+BEGIN_EXAMPLE
-  guix environment -C -m manifest.scm \
-       -E GUIX_LOCPATH -E LANG --share=$HOME/.guix-profile/lib/locale \
+  guix shell -C -m manifest.scm \
+       -E GUIX_LOCPATH -E LANG --share=$GUIX_LOCPATH \
        -- haunt build
 #+END_EXAMPLE
 
@@ -25,8 +25,8 @@ To try out the website locally while you work on it, run the following
 command:
 
 #+BEGIN_EXAMPLE
-  guix environment -C -N -m manifest.scm \
-       -E GUIX_LOCPATH -E LANG --share=$HOME/.guix-profile/lib/locale \
+  guix shell -C -N -m manifest.scm \
+       -E GUIX_LOCPATH -E LANG --share=$GUIX_LOCPATH \
        -- haunt serve -w
 #+END_EXAMPLE