Add Web Emulator

[GreenFuze]

Summary

Adds Web Emulator, a generic Playnite add-on that registers managed browser-emulator profiles backed by EmulatorJS, js-dos, and ScummVM WebAssembly.

Release verification

• Public source repository and Apache-2.0 project license
• Public v0.1.0 release with a Playnite .pext package
• Installer and add-on manifests pass Playnite Toolbox verification
• Third-party emulator credits, source links, and license restrictions are included in the package and exposed in Playnite
• Catalog user agreement discloses first-use runtime downloads and the non-commercial Snes9x, PicoDrive, and MAME 2003-Plus terms
• The add-on package contains no emulator runtime binaries, games, ROMs, firmware, or BIOS files
• Release build succeeds with zero warnings and all 13 tests pass