[ci] Add CI spelling check and fix spelling errors (#8882)

reviewdog/action-misspell is used on frc-docs. It has a dictionary of
commonly misspelled words, so it has less false positives then other
tools.

wpimath/src/main/java/org/wpilib/math/optimization/Problem.java

@@ -108,7 +108,7 @@ public class Problem implements AutoCloseable {
    * <p>Decision variables have an initial value of zero.
    *
    * @param rows Number of matrix rows.
-   * @return A symmetric matrix of decision varaibles in the optimization problem.
+   * @return A symmetric matrix of decision variables in the optimization problem.
    */
   public VariableMatrix symmetricDecisionVariable(int rows) {
     return new VariableMatrix(rows, rows, ProblemJNI.symmetricDecisionVariable(m_handle, rows));

wpimath/src/main/java/org/wpilib/math/optimization/ProblemJNI.java

@@ -40,7 +40,7 @@ final class ProblemJNI extends WPIMathJNI {
    *
    * @param handle Problem handle.
    * @param rows Number of matrix rows.
-   * @return A symmetric matrix of decision varaibles in the optimization problem.
+   * @return A symmetric matrix of decision variables in the optimization problem.
    */
   static native long[] symmetricDecisionVariable(long handle, int rows);
 

wpimath/src/main/native/include/wpi/math/controller/PIDController.hpp

@@ -229,7 +229,7 @@ class WPILIB_DLLEXPORT PIDController
 
   /**
    * Returns true if the error is within the tolerance of the setpoint.
-   * The error tolerance defauls to 0.05, and the error derivative tolerance
+   * The error tolerance defaults to 0.05, and the error derivative tolerance
    * defaults to ∞.
    *
    * This will return false until at least one input value has been computed.