Select Color: built-in RAL CLASSIC and CSS COLORS color books

Two AutoCAD .acb books ship with the panel and are read the first time it
opens in a session; a loaded book of the same name replaces them. RAL
values are approximate (CC BY-SA 4.0, Wikipedia); sources and licences
are in each file's header and assets/color_books/README.md.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_013rGmDUNr1hUf4zo1X3dak8

src/ui/color_select/book.rs

@@ -57,6 +57,17 @@ impl ColorBook {
     }
 }
 
+/// The colour books that ship with the program; their licences are in the
+/// files' header comments.
+pub fn builtin() -> impl Iterator<Item = ColorBook> {
+    [
+        include_str!("../../../assets/color_books/ral-classic.acb"),
+        include_str!("../../../assets/color_books/css-colors.acb"),
+    ]
+    .into_iter()
+    .filter_map(|text| parse(text).ok())
+}
+
 /// Read an `.acb` file's text.
 pub fn parse(text: &str) -> Result<ColorBook, String> {
     let doc = roxmltree::Document::parse(text.trim_start_matches('\u{feff}'))