Document sprite index file's sdf property (#356)

docs/src/routes/sprite/index.tsx

@@ -40,6 +40,7 @@ Apart from the required \`width\`, \`height\`, \`x\`, and \`y\` properties, the
 - \`content\`: An array of four numbers, with the first two specifying the left, top corner, and the last two specifying the right, bottom corner. If present, and if the icon uses [\`icon-text-fit\`](${import.meta.env.BASE_URL}layers/#layout-symbol-icon-text-fit), the symbol's text will be fit inside the content box.
 - \`stretchX\`: An array of two-element arrays, consisting of two numbers that represent the _from_ position and the _to_ position of areas that can be stretched.
 - \`stretchY\`: Same as \`stretchX\`, but for the vertical dimension.
+- \`sdf\`: Boolean. If \`true\` then the image is handled as a signed-distance field (SDF) and its color can be set at runtime using the [\`icon-color\`](${import.meta.env.BASE_URL}layers/#paint-symbol-icon-color) and [\`icon-halo-color\`](${import.meta.env.BASE_URL}layers/#paint-symbol-icon-halo-color) properties. Defaults to \`false\`.
 
 MapLibre SDKs will use the value of the \`sprite\` property in the style to generate the URLs for loading both files. First, for both file types, it will append \`@2x\` to the URL on high-DPI devices. Second, it will append a file extension: \`.json\` for the index file, and \`.png\` for the image file. For example, if you specified \`"sprite": "https://example.com/sprite"\`, renderers would load \`https://example.com/sprite.json\` and \`https://example.com/sprite.png\`, or \`https://example.com/sprite@2x.json\` and \`https://example.com/sprite@2x.png\`.
 

src/reference/v8.json

@@ -5208,7 +5208,7 @@
       "type": "color",
       "default": "#000000",
       "transition": true,
-      "doc": "The color of the icon. This can only be used with sdf icons.",
+      "doc": "The color of the icon. This can only be used with SDF icons.",
       "requires": [
         "icon-image"
       ],