Update README and configuration for Ruby 3.2 compatibility; enhance unit methods with keyword arguments

Author: olbrich

README.md

@@ -25,6 +25,8 @@ manipulations to ensure an accurate result.
 
 ## Installation
 
+This package requires Ruby 3.2 or later.
+
 This package may be installed using:
 
 ```bash
@@ -52,6 +54,7 @@ unit = "1 mm".to_unit                # convert string object
 unit = object.to_unit                # convert any object using object.to_s
 unit = Unit.new('1/4 cup')           # Rational number
 unit = Unit.new('1+1i mm')           # Complex Number
+unit = Unit.new(scalar: 1.5, numerator: ["<meter>"], denominator: ["<second>"])  # keyword arguments
 ```
 
 ### Rules

lib/ruby_units/configuration.rb

@@ -46,9 +46,9 @@ class Configuration
     #
     # @param separator [Boolean] whether to include a space between the scalar and the unit (default: true)
     # @param format [Symbol] the format to use when generating output (default: :rational)
-    # @param ** [Hash] additional keyword arguments (ignored, for forward compatibility)
+    # @param **_options [Hash] additional keyword arguments (ignored, for forward compatibility)
     # @return [Configuration] a new configuration instance
-    def initialize(separator: true, format: :rational, **)
+    def initialize(separator: true, format: :rational, **_options)
       self.separator = separator
       self.format = format
     end

lib/ruby_units/unit.rb

@@ -544,7 +544,7 @@ def initialize(*options)
         @scalar      = date.ajd
         @numerator   = ["<day>"]
         @denominator = UNITY_ARRAY
-      in /^\s*$/ => empty
+      in /^\s*$/ => _empty
         raise ArgumentError, "No Unit Specified"
       in String => str
         parse(str)
@@ -1341,13 +1341,18 @@ def abs
     end
 
     # ceil of a unit
+    # Forwards all arguments to the scalar's ceil method
+    # @param args [Array] arguments to pass to the scalar's ceil method (e.g., number of decimal digits)
     # @return [Numeric,Unit]
     def ceil(...)
       return @scalar.ceil(...) if unitless?
 
       self.class.new(scalar: @scalar.ceil(...), numerator: @numerator, denominator: @denominator)
     end
 
+    # Floor of a unit
+    # Forwards all arguments to the scalar's floor method
+    # @param args [Array] arguments to pass to the scalar's floor method (e.g., number of decimal digits)
     # @return [Numeric,Unit]
     def floor(...)
       return @scalar.floor(...) if unitless?
@@ -1360,17 +1365,22 @@ def floor(...)
     # Rational, etc..). Because unit conversions can often result in Rational
     # scalars (to preserve precision), it may be advisable to use +to_s+ to
     # format output instead of using +round+.
+    # Forwards all arguments to the scalar's round method
     # @example
     #   RubyUnits::Unit.new('21870 mm/min').convert_to('m/min').round(1) #=> 2187/100 m/min
     #   RubyUnits::Unit.new('21870 mm/min').convert_to('m/min').to_s('%0.1f') #=> 21.9 m/min
     #
+    # @param args [Array] arguments to pass to the scalar's round method (e.g., number of decimal digits, mode)
     # @return [Numeric,Unit]
     def round(...)
       return @scalar.round(...) if unitless?
 
       self.class.new(scalar: @scalar.round(...), numerator: @numerator, denominator: @denominator)
     end
 
+    # Truncate the unit according to the scalar's truncate method
+    # Forwards all arguments to the scalar's truncate method
+    # @param args [Array] arguments to pass to the scalar's truncate method (e.g., number of decimal digits)
     # @return [Numeric, Unit]
     def truncate(...)
       return @scalar.truncate(...) if unitless?