Ensure fallbacks are emitted as CSS variables too

Author: philipp-spiess

packages/@tailwindcss-postcss/src/__snapshots__/index.test.ts.snap

@@ -10,11 +10,11 @@ exports[`\`@import 'tailwindcss'\` is replaced with the generated CSS 1`] = `
     --text-2xl--line-height: calc(2 / 1.5);
     --font-weight-bold: 700;
     --default-font-family: var(--font-sans);
-    --default-font-feature-settings: var(--font-sans--font-feature-settings);
-    --default-font-variation-settings: var(--font-sans--font-variation-settings);
+    --default-font-feature-settings: var(--font-sans--font-feature-settings, normal);
+    --default-font-variation-settings: var(--font-sans--font-variation-settings, normal);
     --default-mono-font-family: var(--font-mono);
-    --default-mono-font-feature-settings: var(--font-mono--font-feature-settings);
-    --default-mono-font-variation-settings: var(--font-mono--font-variation-settings);
+    --default-mono-font-feature-settings: var(--font-mono--font-feature-settings, normal);
+    --default-mono-font-variation-settings: var(--font-mono--font-variation-settings, normal);
   }
 }
 
@@ -37,9 +37,9 @@ exports[`\`@import 'tailwindcss'\` is replaced with the generated CSS 1`] = `
     -webkit-text-size-adjust: 100%;
     tab-size: 4;
     line-height: 1.5;
-    font-family: var(--default-font-family, ui-sans-serif, system-ui, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji");
-    font-feature-settings: var(--default-font-feature-settings, normal);
-    font-variation-settings: var(--default-font-variation-settings, normal);
+    font-family: var(--default-font-family);
+    font-feature-settings: var(--default-font-feature-settings);
+    font-variation-settings: var(--default-font-variation-settings);
     -webkit-tap-highlight-color: transparent;
   }
 
@@ -76,9 +76,9 @@ exports[`\`@import 'tailwindcss'\` is replaced with the generated CSS 1`] = `
   }
 
   code, kbd, samp, pre {
-    font-family: var(--default-mono-font-family, ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace);
-    font-feature-settings: var(--default-mono-font-feature-settings, normal);
-    font-variation-settings: var(--default-mono-font-variation-settings, normal);
+    font-family: var(--default-mono-font-family);
+    font-feature-settings: var(--default-mono-font-feature-settings);
+    font-variation-settings: var(--default-mono-font-variation-settings);
     font-size: 1em;
   }