Fix/windows supported frontend

[hari-silvers]

Description

Before:

After :

• Modified the Linux-only shell commands (mkdir -p, cp) in wireit copy-spec with Node-based cross-platform commands (mkdirp, cpy-cli).
• This allows npm run build to succeed on Windows, Git Bash, WSL, and Linux.
• I have installed two packages(mkdirp, cpy-cli), so there will be changes in the package-lock.json file too and committed those changes too.

Pre-launch Checklist

• I signed the [CLA].
• I read the [Contributors Guide].
• I read the [Style Guide].
• I have added updates to the [CHANGELOG].
• I updated/added relevant documentation.
• My code changes (if any) have tests.

[gemini-code-assist]

Code Review

This pull request is a great improvement for cross-platform compatibility, replacing shell-specific commands with Node.js-based alternatives. The changes are clear and well-described. My review includes a critical point about the required Node.js version introduced by a new dependency, which could impact compatibility. I've also added a suggestion regarding automated testing for these build changes to align with the repository's style guide and ensure long-term stability.

[gspencergoog]

It looks like there are extra directories that you didn't mean to commit in the renderers/lit/src/v0_8 and renderers/lit/src/0_8 directories.

[ava-cassiopeia]

It looks like there are extra directories that you didn't mean to commit in the renderers/lit/src/v0_8 and renderers/lit/src/0_8 directories.

Please fix, and I can re-review after that.