tabspaces: Theme tabspaces-session-file

Tabspaces (https://github.com/mclear-tools/tabspaces) leverages the
tab-bar feature to create buffer-isolated workspaces called
tabspaces. The tabspaces-session-file is used for persisting tabspace
configuration across emacs restarts.  The default configuration is to
save the session file as 'tabsession.el' in the
user-emacs-directory. This is an s-expressions file.  This is the only
data file written by the package.

no-littering.el

@@ -420,6 +420,7 @@ This variable has to be set before `no-littering' is loaded.")
     (setq spell-fu-directory               (var "spell-fu/"))
     (setq svg-lib-icons-dir                (var "svg-lib/icons/"))
     (setq sx-cache-directory               (var "sx/cache/"))
+    (setq tabspaces-session-file           (var "tabspaces-session.eld"))
     (setq tldr-directory-path              (var "tldr/"))
     (setq transient-history-file           (var "transient/history.el"))
     (setq transient-levels-file            (etc "transient/levels.el"))