fix(arch): add support for Windows arm64

[advait-m]

Problem

On a native Windows arm64 runner, the action fails outright:

Installing sentry-cli version latest
Error: TypeError: Unsupported platform: win32/arm64

PLATFORM_MAPPINGS in src/get-download-link.ts has entries for win32-x32 and win32-x64, but none for win32-arm64, and the only fallback covers darwin:

if (!platform && process.platform === 'darwin') {
  // Fallback to universal build if there is match on MacOS architecture
  platform = 'Darwin-universal';
}

if (!platform) {
  throw new TypeError(`Unsupported platform: ${process.platform}/${process.arch}`);
}

This is increasingly easy to hit now that GitHub offers native Windows arm64 runners — anything that previously cross-compiled to arm64 on an x64 host (where process.arch was x64) breaks when moved onto a native arm64 host.

Fix

sentry-cli already publishes a Windows aarch64 binary next to the i686 and x86_64 ones, so this only needs the mapping entry:

'win32-arm64': 'Windows-aarch64',

This mirrors how linux-arm64 maps to Linux-aarch64.

Verified the asset exists and is the right architecture:

$ curl -sI https://downloads.sentry-cdn.com/sentry-cli/latest/sentry-cli-Windows-aarch64.exe | head -1
HTTP/2 200

$ file sentry-cli-Windows-aarch64.exe
sentry-cli-Windows-aarch64.exe: PE32+ executable (console) Aarch64, for MS Windows

Changes

• src/get-download-link.ts — the mapping entry (the actual fix).
• dist/main.js / dist/main.js.map — rebuilt with pnpm build, since the bundle is committed and is what action.yml runs. The only semantic change in the bundle is the new mapping entry.
• README.md — added the win32 / arm64 (aarch64) row to the supported-architecture table.

I confirmed dist/ rebuilds byte-for-byte from unmodified main before making the change, so the bundle diff here is purely this fix and not build-environment drift.

pnpm lint and pnpm typecheck both pass.

I left CHANGELOG.md alone since entries there look like they're added per release rather than per PR — happy to add one if you'd prefer.
.

[advait-m]

@matbour tagging you for review - thank you!