Support giving color values as percentage

Sources/LibMakeColors/Model/Scanner+ColorParser.swift

@@ -119,13 +119,25 @@ extension Scanner {
     func commaSeparated() -> [UInt8]? {
         var result: [UInt8] = []
         repeat {
-            guard let int = scanInt(), let component = UInt8(exactly: int) else {
+            guard let component = self.component() else {
                 return nil
             }
             result.append(component)
         } while string(",")
         return result
     }
+
+    func component() -> UInt8? {
+        guard var int = scanInt() else {
+            return nil
+        }
+
+        if string("%") {
+            int = int * 0xFF / 100
+        }
+
+        return UInt8(exactly: int)
+    }
 }
 
 private extension Scanner {

Tests/MakeColorsTests/ColorParserTest.swift

@@ -57,6 +57,35 @@ final class ColorParserTest: XCTestCase {
         XCTAssertNil(color)
     }
 
+    func testScanningColorWithPercentage() throws {
+        let color = scanColor("rgba(100%, 0, 50%, 100%)")
+        XCTAssertEqual(color, Color(red: 255, green: 0, blue: 127, alpha: 255))
+    }
+
+    func testReadingComponentAsByte() throws {
+        let scanner = Scanner(string: "128")
+        XCTAssertEqual(scanner.component(), 128)
+        XCTAssertTrue(scanner.isAtEnd)
+    }
+
+    func testReadingComponentAs100Percent() throws {
+        let scanner = Scanner(string: "100%")
+        XCTAssertEqual(scanner.component(), 0xFF)
+        XCTAssertTrue(scanner.isAtEnd)
+    }
+
+    func testReadingComponentAs0Percent() throws {
+        let scanner = Scanner(string: "0%")
+        XCTAssertEqual(scanner.component(), 0)
+        XCTAssertTrue(scanner.isAtEnd)
+    }
+
+    func testReadingComponentAs50PercentRoundsDown() throws {
+        let scanner = Scanner(string: "50%")
+        XCTAssertEqual(scanner.component(), 127)
+        XCTAssertTrue(scanner.isAtEnd)
+    }
+
     private func scanColor(_ input: String) -> Color? {
         let scanner = Scanner(string: input)
         return scanner.color()