Add authorsaddresses field to acmart

This was added in a recent version of the acmart style and is
required to set (or remove) the addresses field at the bottom of
the first page in some styles.

scribble-doc/scribblings/scribble/acmart.scrbl

@@ -203,6 +203,23 @@ screen version of the image links to the badge authority.
   @abstract{This is an abstract.}
 }|
 
+@defproc[(authorsaddresses [addresses pre-content?] ...) block?]{
+ Sets the text for the authors' addresses on the first page
+ in some styles. By default this field is set to the authors
+ and their affiliation information.
+
+ The @racket[addresses] parameter takes the address text. As a
+ special case the empty list removes the addresses field entirely.
+
+ @codeblock|{
+  #lang scribble/acmart @acmsmall
+  @title{A fancy paper}
+  @author["Ronon Dex"]
+  @authorsaddresses{}
+}|
+
+ @history[#:added "1.26"]}
+
 @deftogether[(
 @defproc[(terms [content pre-content?] ...) content?]
 @defproc[(keywords [content pre-content?] ...) content?]

scribble-lib/scribble/acmart.rkt

@@ -45,6 +45,10 @@
                #:email (or/c pre-content? email? (listof email?) #f))
               #:rest (listof pre-content?)
               block?)]
+ [authorsaddresses (->* ()
+                        ()
+                        #:rest (listof pre-content?)
+                        block?)]
  [institution (->* ()
                    (#:departments (listof (or/c pre-content? institution?)))
                    #:rest pre-content?
@@ -282,7 +286,13 @@
                                                   [else
                                                    (for/list ([e (in-list email)])
                                                      (convert-email e))]))))))))
-  
+
+(define (authorsaddresses . content)
+  (make-paragraph
+   (make-style 'pretitle command-props)
+   (make-element (make-style "authorsaddresses" command-props)
+                 (decode-content content))))
+
 (define (institution #:departments [departments '()]
                      . name)
   (author-institution name departments))