fixup! Add Number#humanize

Add doc for significant

src/number.cr

@@ -234,7 +234,7 @@ struct Number
 
   # SI prefixes used by `#humanize`. Equal to `SI_PREFIXES` but prepends the
   # prefix with a space charater.
-  SI_PREFIXES_PADDED = ->(magnitude : Int32, number : Float64) do
+  SI_PREFIXES_PADDED = ->(magnitude : Int32, _number : Float64) do
     magnitude = Number.prefix_index(magnitude)
     {magnitude, (magnitude == 0 ? " " : si_prefix(magnitude))}
   end
@@ -266,8 +266,15 @@ struct Number
   # By default, SI prefixes are used (see `SI_PREFIXES`).
   #
   # ```
-  # 1_200_000_000.humanize                                   # => "1.2G"
-  # 0.000_000_012.humanize                                   # => "12n"
+  # 1_200_000_000.humanize # => "1.2G"
+  # 0.000_000_012.humanize # => "12n"
+  # ```
+  #
+  # If *significant* is `false`, the number of *precision* digits is preserved
+  # after the decimal separator.
+  #
+  # ```
+  # 1_234.567_890.humanize(precision: 2)                     # => "1.2k"
   # 1_234.567_890.humanize(precision: 2, significant: false) # => "1.23k"
   # ```
   #
@@ -302,8 +309,15 @@ struct Number
   # By default, SI prefixes are used (see `SI_PREFIXES`).
   #
   # ```
-  # 1_200_000_000.humanize                                   # => "1.2G"
-  # 0.000_000_012.humanize                                   # => "12n"
+  # 1_200_000_000.humanize # => "1.2G"
+  # 0.000_000_012.humanize # => "12n"
+  # ```
+  #
+  # If *significant* is `false`, the number of *precision* digits is preserved
+  # after the decimal separator.
+  #
+  # ```
+  # 1_234.567_890.humanize(precision: 2)                     # => "1.2k"
   # 1_234.567_890.humanize(precision: 2, significant: false) # => "1.23k"
   # ```
   #