Treat float values as atoms in CSS

Otherwise we treat `0.5em` as two atoms, unlike `1em` which was
already a single atom.

CHANGELOG.md

@@ -11,6 +11,8 @@ Expanded filename associations, so difftastic recognises more files.
 Improved parsing for regex and template string literals in JavaScript
 and TypeScript.
 
+Improved parsing for float values in CSS.
+
 Improved word diffing on punctuation in comments.
 
 When logging is enabled (e.g. `RUST_LOG=warn`), difftastic now warns

sample_files/css_after.css

@@ -13,3 +13,7 @@ world */
   color: blue;
   font-family: "After";
 }
+
+.another {
+  margin-left: 1em;
+}

sample_files/css_before.css

@@ -12,3 +12,7 @@ world */
   color: yellow;
   font-family: "Before";
 }
+
+.another {
+  margin-left: 0.5em;
+}

src/tree_sitter_parser.rs

@@ -136,7 +136,7 @@ pub fn from_extension(extension: &OsStr) -> Option<TreeSitterConfig> {
         "css" => Some(TreeSitterConfig {
             name: "CSS",
             language: unsafe { tree_sitter_css() },
-            atom_nodes: (vec!["integer_value"]).into_iter().collect(),
+            atom_nodes: (vec!["integer_value", "float_value"]).into_iter().collect(),
             delimiter_tokens: (vec![("{", "}"), ("(", ")")]),
             highlight_queries: include_str!("../vendor/highlights/css.scm"),
         }),