Split up documentation (#632)

Closes: #558

docs/customization.md

@@ -0,0 +1,70 @@
+# Customization
+
+This document covers advanced customization options including checksum validation, custom manifests, and problem matchers.
+
+## Validate checksum
+
+You can specify a checksum to validate the downloaded executable. Checksums up to the default version
+are automatically verified by this action. The sha256 hashes can be found on the
+[releases page](https://github.com/astral-sh/uv/releases) of the uv repo.
+
+```yaml
+- name: Install a specific version and validate the checksum
+  uses: astral-sh/setup-uv@v6
+  with:
+    version: "0.3.1"
+    checksum: "e11b01402ab645392c7ad6044db63d37e4fd1e745e015306993b07695ea5f9f8"
+```
+
+## Manifest file
+
+The `manifest-file` input allows you to specify a JSON manifest that lists available uv versions,
+architectures, and their download URLs. By default, this action uses the manifest file contained
+in this repository, which is automatically updated with each release of uv.
+
+The manifest file contains an array of objects, each describing a version,
+architecture, platform, and the corresponding download URL. For example:
+
+```json
+[
+  {
+    "version": "0.7.13",
+    "artifactName": "uv-aarch64-apple-darwin.tar.gz",
+    "arch": "aarch64",
+    "platform": "apple-darwin",
+    "downloadUrl": "https://github.com/astral-sh/uv/releases/download/0.7.13/uv-aarch64-apple-darwin.tar.gz"
+  },
+  ...
+]
+```
+
+You can supply a custom manifest file URL to define additional versions,
+architectures, or different download URLs.
+This is useful if you maintain your own uv builds or want to override the default sources.
+
+```yaml
+- name: Use a custom manifest file
+  uses: astral-sh/setup-uv@v6
+  with:
+    manifest-file: "https://example.com/my-custom-manifest.json"
+```
+
+> [!NOTE]
+> When you use a custom manifest file and do not set the `version` input, its default value is `latest`.
+> This means the action will install the latest version available in the custom manifest file.
+> This is different from the default behavior of installing the latest version from the official uv releases.
+
+## Add problem matchers
+
+This action automatically adds
+[problem matchers](https://github.com/actions/toolkit/blob/main/docs/problem-matchers.md)
+for python errors.
+
+You can disable this by setting the `add-problem-matchers` input to `false`.
+
+```yaml
+- name: Install the latest version of uv without problem matchers
+  uses: astral-sh/setup-uv@v6
+  with:
+    add-problem-matchers: false
+```