theo: Fix npm warning about tmp setting

`NPM_CONFIG_TMP` variable triggered annoying warning for every invocation of any `npm` command:

    npm WARN config tmp This setting is no longer used.  npm stores temporary files in a special
    npm WARN config location in the cache, and they are managed by
    npm WARN config     [`cacache`](http://npm.im/cacache).

While at it, let’s also manage the npm config with home-manager and move the cache path setting to there.

common/data/config.fish

@@ -15,9 +15,7 @@ set -x CARGO_HOME $XDG_DATA_HOME/cargo
 set -x CCACHE_DIR $XDG_CACHE_HOME/ccache
 set -x GNUPGHOME $XDG_DATA_HOME/gnupg
 set -x GTK2_RC_FILES $XDG_CONFIG_HOME/gtk-2.0/gtkrc
-set -x NPM_CONFIG_USERCONFIG $XDG_CONFIG_HOME/npm/config
-set -x NPM_CONFIG_CACHE $XDG_CACHE_HOME/npm
-set -x NPM_CONFIG_TMP $XDG_RUNTIME_DIR/npm
+set -x NPM_CONFIG_USERCONFIG $XDG_CONFIG_HOME/npm/npmrc
 set -x RUSTUP_HOME $XDG_DATA_HOME/rustup
 set -x STACK_ROOT $XDG_DATA_HOME/stack
 set -x WEECHAT_HOME $XDG_CONFIG_HOME/weechat

hosts/theo/configuration.nix

@@ -557,6 +557,11 @@ in {
       };
     };
 
+    home.file.".config/npm/npmrc".text = ''
+      prefix=''${XDG_DATA_HOME}/npm
+      cache=''${XDG_CACHE_HOME}/npm
+    '';
+
     home.file.".config/mozc/ibus_config.textproto".text = ''
       # `ibus write-cache; ibus restart` might be necessary to apply changes.
       engines {