docs: add DashboardSettings.md documenting DriverStationDashboardSettings.json

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Co-authored-by: ThadHouse <7727148+ThadHouse@users.noreply.github.com>

Author: Copilot

docs/DashboardSettings.md

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+# Dashboard Settings
+
+The FIRST Driver Station supports configuring custom dashboards and overriding the default WPILib year used for dashboard lookups. This is done via a JSON configuration file named `DriverStationDashboardSettings.json`.
+
+## File Location
+
+Place the file in the DS configuration directory:
+
+- **Windows**: `C:\Users\Public\Documents\FIRSTDriverStation\DriverStationDashboardSettings.json`
+- **Unix (Linux/macOS)**: `~/.firstds/DriverStationDashboardSettings.json`
+
+## Configuration
+
+The file is a JSON object with two optional top-level keys: `CustomDashboards` and `DashboardYearOverrides`.
+
+```json
+{
+  "CustomDashboards": [
+    { "Name": "CoolDash1", "Executable": "C:\\Dashboards\\CoolDash1App" },
+    { "Name": "ExtraDash", "Executable": "C:\\Dashboards\\ExtraDashApp" }
+  ],
+  "DashboardYearOverrides": [
+    { "DashboardYearToOverride": "2027_alpha5", "DashboardOverrideYear": "2027_alpha6" }
+  ]
+}
+```
+
+### CustomDashboards
+
+`CustomDashboards` is an array of custom dashboards to add to the dashboard selector in the DS. Each entry has the following fields:
+
+| Field        | Type   | Description                                             |
+|--------------|--------|---------------------------------------------------------|
+| `Name`       | string | The display name shown in the DS dashboard selector.    |
+| `Executable` | string | The full path to the dashboard executable to launch.    |
+
+### DashboardYearOverrides
+
+`DashboardYearOverrides` is an array of WPILib year overrides that redirect the DS when looking up default dashboards for a given year. Each entry has the following fields:
+
+| Field                    | Type   | Description                                                   |
+|--------------------------|--------|---------------------------------------------------------------|
+| `DashboardYearToOverride`| string | The WPILib year string whose dashboard location is overridden. |
+| `DashboardOverrideYear`  | string | The WPILib year string to use instead when locating dashboards.|