[circt-verilog-lsp][vscode] Add initial VS Code extension configuration for CIRCT Verilog LSP

[uenoku]

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This commit adds the basic configuration files needed for a VS Code extension that provides Verilog language server protocol (LSP) support through CIRCT.

While it may seem unusual to include a VS Code extension in-tree, this follows the precedent set by the MLIR VS Code extension (https://github.com/llvm/llvm-project/tree/main/mlir/utils/vscode). Having the extension in-tree ensures it stays in sync with the server implementation and simplifies maintenance.

The extension will enable VS Code to communicate with the CIRCT Verilog LSP server, providing features like syntax highlighting, error checking, and code navigation for Verilog files (.v and .sv).