Merge branch 'ngae-margin-work' into 'main'

...n/java/gov/usgs/earthquake/nshmp/gmm/ChapmanGuo_2021.java

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

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

...ava/gov/usgs/earthquake/nshmp/gmm/GroundMotionTables.java

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

.../java/gov/usgs/earthquake/nshmp/gmm/PezeshkEtAl_2018.java

.../gov/usgs/earthquake/nshmp/gmm/ShahjoueiPezeshk_2016.java

src/main/resources/gmm/coeffs/nga-east-usgs-siteamp.csv

...test/java/gov/usgs/earthquake/nshmp/gmm/NgaEastTests.java