update developer notes re: coefficient updates from Kuehn's GitHub

src/main/java/gov/usgs/earthquake/nshmp/gmm/KuehnEtAl_2020.java

@@ -92,7 +92,16 @@ public abstract class KuehnEtAl_2020 implements GroundMotionModel {
    *
    * seattle() indicates site inside Seattle polygon and deep M9 scaling
    *
-   * Kuehn Cascadia models automatically include Kuehn Seattle behavior
+   * Kuehn Cascadia models automatically include Kuehn Seattle behavior (is this
+   * accurate?)
+   *
+   * Coefficients for Alaska (theta_1_slab_reg_Al, theta_1_if_reg_Al,
+   * theta_7_reg_Al, theta_6_2_reg_Al) and mean_redisual_seattle_basin updated
+   * based on Kuehn's GitHub repository <a href=
+   * "https://github.com/nikuehn/KBCG20/blob/5d30338436b897822b411553c6ae0bf31fac5ce5/COEFFS_SEP21/coefficients_KBCG20.csv">
+   * https://github.com/nikuehn/KBCG20/blob/
+   * 5d30338436b897822b411553c6ae0bf31fac5ce5/COEFFS_SEP21/coefficients_KBCG20.
+   * csv</a>
    */
 
   static final String NAME = "Kuehn et al. (2020)";