Install witr in the devcontainer

[Copilot]

Adds the witr CLI ("why is this running?") to the devcontainer.

witr ships as a single static Go binary, so this uses the gh-release feature—consistent with how other tools in this container are provisioned—to fetch the released Linux binary and place it on PATH (/usr/local/bin/witr), tracking the latest release.

Changes

• .devcontainer/devcontainer.json: add the gh-release feature targeting pranshuparmar/witr.
  • assetRegex pins selection to the raw witr-linux-amd64/witr-linux-arm64 binary, disambiguating from the .deb/.rpm/.apk packages that share the same arch suffix.

"ghcr.io/devcontainers-extra/features/gh-release:1": {
  "repo": "pranshuparmar/witr",
  "binaryNames": "witr",
  "assetRegex": "^witr-linux-(amd64|arm64)$"
}