Adds ascii_title to string manipulation

docs/content/manual/v1.7/manual.yml

@@ -1824,7 +1824,7 @@ sections:
             input: '["a",1,2.3,true,null,false]'
             output: ['"a 1 2.3 true  false"']
 
-      - title: "`ascii_downcase`, `ascii_upcase`"
+      - title: "`ascii_downcase`, `ascii_upcase`, `ascii_title`"
         body: |
 
           Emit a copy of the input string with its alphabetic characters (a-z and A-Z)
@@ -1834,6 +1834,9 @@ sections:
           - program: "ascii_upcase"
             input: '"useful but not for é"'
             output: ['"USEFUL BUT NOT FOR é"']
+          - program: "ascii_title"
+            input: '"useful but not for é"'
+            output: ['"Useful But Not For é"']
 
       - title: "`while(cond; update)`"
         body: |

src/builtin.jq

@@ -203,6 +203,8 @@ def ascii_downcase:
 # like ruby's upcase - only characters a to z are affected
 def ascii_upcase:
   explode | map( if 97 <= . and . <= 122 then . - 32  else . end) | implode;
+def ascii_title:
+  ascii_downcase | split(" ") | map(sub("(?<a>.)"; "\(.a|ascii_upcase)")) | join(" ")
 
 # Streaming utilities
 def truncate_stream(stream):