fix: Add enum for format parameter (#220)

# Description

Add a list of allowable strings as an enum type for the format
parameter.

## Issue Ticket Number

Fixes #142 

## Type of change

<!-- Please select all options that are applicable. -->

- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] Fix or improve the documentation
- [ ] This change requires a documentation update

# Checklist

<!-- These must all be followed and checked. -->

- [x] I have followed the contributing guidelines of this project as
mentioned in [CONTRIBUTING.md](/CONTRIBUTING.md)
- [x] I have created an
[issue](https://github.com/colbyfayock/cloudinary-util/issues) ticket
for this PR
- [x] I have checked to ensure there aren't other open [Pull
Requests](https://github.com/colbyfayock/cloudinary-util/pulls) for the
same update/change?
- [x] I have performed a self-review of my own code
- [ ] I have run tests locally to ensure they all pass
- [x] I have commented my code, particularly in hard-to-understand areas
- [ ] I have made corresponding changes needed to the documentation

Author: saai-syvendra

packages/url-loader/src/types/asset.ts

@@ -45,7 +45,36 @@ export const assetOptionsSchema = z.object({
     )
     .optional(),
   format: z
-    .string()
+    .enum([
+      "auto",
+      "auto:image",
+      "auto:animated",
+      "gif",
+      "png",
+      "jpg",
+      "bmp",
+      "ico",
+      "pdf",
+      "tiff",
+      "eps",
+      "jpc",
+      "jp2",
+      "psd",
+      "webp",
+      "zip",
+      "svg",
+      "webm",
+      "wdp",
+      "hpx",
+      "djvu",
+      "ai",
+      "flif",
+      "bpg",
+      "miff",
+      "tga",
+      "heic",
+      "default" // library specific feature to turn off automatic optimization
+    ])
     .default("auto")
     .describe(
       JSON.stringify({