Use StringScanner#peek_byte to get double or single quotation mark

## Why?
`StringScanner#peek_byte` is fast, because it does not generate String object.

## Benchmark
```
RUBYLIB= BUNDLER_ORIG_RUBYLIB= /Users/naitoh/.rbenv/versions/3.3.4/bin/ruby -v -S benchmark-driver /Users/naitoh/ghq/github.com/naitoh/rexml/benchmark/parse.yaml
ruby 3.3.4 (2024-07-09 revision be1089c8ec) [arm64-darwin22]
Calculating -------------------------------------
                         before       after  before(YJIT)  after(YJIT)
                 dom     19.896      19.847        35.010       36.082 i/s -     100.000 times in 5.026136s 5.038531s 2.856343s 2.771448s
                 sax     30.249      31.268        54.243       55.914 i/s -     100.000 times in 3.305870s 3.198205s 1.843540s 1.788471s
                pull     34.433      35.661        63.782       68.741 i/s -     100.000 times in 2.904195s 2.804202s 1.567841s 1.454734s
              stream     34.127      35.278        58.097       64.829 i/s -     100.000 times in 2.930236s 2.834602s 1.721255s 1.542522s

Comparison:
                              dom
         after(YJIT):        36.1 i/s
        before(YJIT):        35.0 i/s - 1.03x  slower
              before:        19.9 i/s - 1.81x  slower
               after:        19.8 i/s - 1.82x  slower

                              sax
         after(YJIT):        55.9 i/s
        before(YJIT):        54.2 i/s - 1.03x  slower
               after:        31.3 i/s - 1.79x  slower
              before:        30.2 i/s - 1.85x  slower

                             pull
         after(YJIT):        68.7 i/s
        before(YJIT):        63.8 i/s - 1.08x  slower
               after:        35.7 i/s - 1.93x  slower
              before:        34.4 i/s - 2.00x  slower

                           stream
         after(YJIT):        64.8 i/s
        before(YJIT):        58.1 i/s - 1.12x  slower
               after:        35.3 i/s - 1.84x  slower
              before:        34.1 i/s - 1.90x  slower

```
- YJIT=ON : 1.03x - 1.12x faster
- YJIT=OFF : 1.00x - 1.03x faster

Author: naitoh

lib/rexml/parsers/baseparser.rb

@@ -157,6 +157,11 @@ module Private
           DEFAULT_ENTITIES_PATTERNS[term] = /&#{term};/
         end
         XML_PREFIXED_NAMESPACE = "http://www.w3.org/XML/1998/namespace"
+
+        QUOTE = [].tap { |x|
+          x['"'.ord] = '"'
+          x["'".ord] = "'"
+        }
       end
       private_constant :Private
 
@@ -766,6 +771,19 @@ def process_instruction
         [:processing_instruction, name, content]
       end
 
+      if StringScanner::Version < "3.1.1"
+        def get_quote
+          @source.match(/(['"])/, true)&.[](1)
+        end
+      else
+        def get_quote
+          if quote = Private::QUOTE[@source.peek_byte]
+            @source.scan_byte
+          end
+          quote
+        end
+      end
+
       def parse_attributes(prefixes)
         attributes = {}
         expanded_names = {}
@@ -785,11 +803,10 @@ def parse_attributes(prefixes)
               message = "Missing attribute equal: <#{name}>"
               raise REXML::ParseException.new(message, @source)
             end
-            unless match = @source.match(/(['"])/, true)
+            unless quote = get_quote
               message = "Missing attribute value start quote: <#{name}>"
               raise REXML::ParseException.new(message, @source)
             end
-            quote = match[1]
             start_position = @source.position
             value = @source.read_until(quote)
             unless value.chomp!(quote)

lib/rexml/source.rb

@@ -158,6 +158,14 @@ def position=(pos)
       @scanner.pos = pos
     end
 
+    def peek_byte
+      @scanner.peek_byte
+    end
+
+    def scan_byte
+      @scanner.scan_byte
+    end
+
     # @return true if the Source is exhausted
     def empty?
       @scanner.eos?