histogram gives back percentage column. (#2340)

crates/nu-cli/src/commands/histogram.rs

@@ -130,6 +130,15 @@ pub async fn histogram(
                 fact.insert_value(&column.item, column_value);
                 fact.insert_untagged("count", UntaggedValue::int(count));
 
+                let percentage = format!(
+                    "{}%",
+                    // Some(2) < the number of digits
+                    // true < group the digits
+                    crate::commands::str_::from::action(&value, &name, Some(2), true)?
+                        .as_string()?
+                );
+                fact.insert_untagged("percentage", UntaggedValue::string(percentage));
+
                 let string = std::iter::repeat("*")
                     .take(value.as_u64().map_err(|_| {
                         ShellError::labeled_error("expected a number", "expected a number", &name)

crates/nu-cli/src/commands/str_/from.rs

@@ -112,7 +112,7 @@ async fn operate(
 }
 
 // TODO If you're using the with-system-locale feature and you're on Windows, Clang 3.9 or higher is also required.
-fn action(
+pub fn action(
     input: &Value,
     tag: impl Into<Tag>,
     digits: Option<u64>,

crates/nu-cli/src/commands/str_/mod.rs

@@ -5,7 +5,7 @@ mod contains;
 mod downcase;
 mod ends_with;
 mod find_replace;
-mod from;
+pub mod from;
 mod index_of;
 mod length;
 mod reverse;