[examples] Add compilable code snippets (#7909)

This enables frc-docs to use RLIs for things that are currently in-line
code blocks, and ensures they compile, which is important with the 2027
breaking changes coming. They are kept separate from the examples to
ensure they don't polute the VSCode examples finder.

Adds the Encoder snippets used in the frc-docs Encoder article as the
first instance of this.

wpilibcExamples/src/main/cpp/snippets/Encoder/cpp/Robot.cpp

@@ -0,0 +1,69 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include <numbers>
+
+#include <frc/Encoder.h>
+#include <frc/TimedRobot.h>
+#include <frc/smartdashboard/SmartDashboard.h>
+#include <wpi/deprecated.h>
+
+/**
+ * Encoder snippets for frc-docs.
+ * https://docs.wpilib.org/en/stable/docs/software/hardware-apis/sensors/encoders-software.html
+ */
+WPI_IGNORE_DEPRECATED
+class Robot : public frc::TimedRobot {
+ public:
+  Robot() {
+    // Configures the encoder to return a distance of 4 for every 256 pulses
+    // Also changes the units of getRate
+    m_encoder.SetDistancePerPulse(4.0 / 256.0);
+    // Configures the encoder to consider itself stopped after .1 seconds
+    m_encoder.SetMaxPeriod(0.1_s);
+    // Configures the encoder to consider itself stopped when its rate is below
+    // 10
+    m_encoder.SetMinRate(10);
+    // Reverses the direction of the encoder
+    m_encoder.SetReverseDirection(true);
+    // Configures an encoder to average its period measurement over 5 samples
+    // Can be between 1 and 127 samples
+    m_encoder.SetSamplesToAverage(5);
+  }
+
+  void TeleopPeriodic() override {
+    // Gets the distance traveled
+    m_encoder.GetDistance();
+
+    // Gets the current rate of the encoder
+    m_encoder.GetRate();
+
+    // Gets whether the encoder is stopped
+    m_encoder.GetStopped();
+
+    // Gets the last direction in which the encoder moved
+    m_encoder.GetDirection();
+
+    // Gets the current period of the encoder
+    m_encoder.GetPeriod();
+
+    // Resets the encoder to read a distance of zero
+    m_encoder.Reset();
+  }
+
+ private:
+  // Initializes an encoder on DIO pins 0 and 1
+  // Defaults to 4X decoding and non-inverted
+  frc::Encoder m_encoder{0, 1};
+
+  // Initializes an encoder on DIO pins 0 and 1
+  // 2X encoding and non-inverted
+  frc::Encoder m_encoder2x{0, 1, false, frc::Encoder::EncodingType::k2X};
+};
+
+#ifndef RUNNING_FRC_TESTS
+int main() {
+  return frc::StartRobot<Robot>();
+}
+#endif

wpilibcExamples/src/main/cpp/snippets/snippets.json

@@ -0,0 +1,12 @@
+[
+  {
+    "name": "Encoder",
+    "description": "Snippets of Encoder class usage for frc-docs.",
+    "tags": [
+      "Hardware",
+      "Encoder"
+    ],
+    "foldername": "Encoder",
+    "gradlebase": "cpp"
+  }
+]