docs: update pattern matcher type

[hyunbinseo]

Describe the bug

Current documentation types the match as follows:

// src/params/fruit.ts

import type { ParamMatcher } from '@sveltejs/kit';

export const match: ParamMatcher = (param): param is 'apple' | 'orange' => {
  return param === 'apple' || param === 'orange';
};

This does not narrow the type beyond string.

// src/routes/archive/[page=fruit]/+page.ts

export const load = ({ params: { page } }) => {
  page; // string
};

To narrow the type - which was implemented in the following PR - the match type should be updated:

• Infer route parameter type from matcher's guard check if applicable #10755

import type { ParamMatcher } from '@sveltejs/kit';

export const match = ((param): param is 'apple' | 'orange' => {
  return param === 'apple' || param === 'orange';
}) satisfies ParamMatcher;

export const load = ({ params: { page } }) => {
  page; // "apple" | "orange"
};

Reproduction

Reference the example code above.

Logs

No response

System Info

System:
  OS: macOS 14.2.1
  CPU: (10) arm64 Apple M1 Pro
  Memory: 116.55 MB / 16.00 GB
  Shell: 5.9 - /bin/zsh
Binaries:
  Node: 20.11.1 - ~/.volta/tools/image/node/20.11.1/bin/node
  npm: 10.2.4 - ~/.volta/tools/image/node/20.11.1/bin/npm
  pnpm: 8.15.4 - ~/.volta/bin/pnpm
Browsers:
  Chrome: 122.0.6261.94
  Edge: 122.0.2365.63
  Safari: 17.2.1
npmPackages:
  @sveltejs/adapter-auto: ^3.0.0 => 3.1.1 
  @sveltejs/kit: ^2.0.0 => 2.5.2 
  @sveltejs/vite-plugin-svelte: ^3.0.0 => 3.0.2 
  svelte: ^4.2.7 => 4.2.12 
  vite: ^5.0.3 => 5.1.5

Severity

annoyance

Additional Information

No response