Fix void `string-join` function error

Upon running `'w3m-session-backup`, this error message would be printed:

    Symbol's function definition is void: string-join

I learned that Emacs doesn't load all functions at load. In particular
for this case, the `string-join` function was in a file not loaded by
default.

Thanks to the following resources:
https://emacs.stackexchange.com/questions/22142/cannot-open-load-file-subr-x
https://github.com/ralesi/ranger.el/blob/9db73d61/ranger.el#L84

I discovered I could require the `subr-x.el` file that contains the
`string-join` function needed. Decided to keep using `string-join`
instead of `(mapconcat 'identity ...` as it reads better in my mind.

0 files changed, 0 insertions, 0 deletions