Add option to disable automatic loading of .vscode/launch.json configurations

## Summary Currently, nvim-dap always includes configurations from `.vscode/launch.json` via the built-in `"dap.launch.json"` config provider. Some users may want to disable this behavior conditionally. ## Use cases - Working on projects where the launch.json is intended for VS Code only - launch.json contains configurations that conflict with nvim-dap setup - Users who want full control over which configurations are available - Loading launch.json only for specific projects ## Current behavior The `"dap.launch.json"` provider is registered in `lua/dap.lua:316-324` and is always called when selecting configurations (via `dap.continue()` or similar). Users can currently disable this by setting the provider to nil: ```lua require('dap').providers.configs["dap.launch.json"] = nil ``` However, this is not documented, feels like an implementation detail rather than a supported API, and doesn't allow for conditional logic. ## Proposed solution Add a setup option that accepts a function, receiving the cwd so users can implement custom logic: ```lua require('dap').setup({ -- Function receives cwd, returns true to load launch.json, false to skip load_launchjs = function(cwd) -- Example: only load for specific projects return vim.fn.filereadable(cwd .. '/.nvim-dap') == 1 end, }) ``` This allows users to: - Disable entirely: `load_launchjs = function() return false end` - Enable only for certain projects based on cwd - Check for marker files, git remotes, etc. For backwards compatibility, the default would be `load_launchjs = function() return true end`. ## Alternatives considered Users could theoretically delete or rename their `.vscode/launch.json`, but this isn't practical when the file is needed for other editors or team members.