updated CHANGELOG.md

Author: gmao-rreichle

CHANGELOG.md

@@ -18,6 +18,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Updated subroutine read_obs_sm_ASCAT_EUMET() to work with both original and revised file name templates. 
 - Updated subroutines read_obs_sm_ASCAT_EUMET(), read_obs_SMAP_halforbit_Tb(), read_obs_SMOS() and read_obs_MODIS_SCF() with hardcoded time ranges for when observations are available and should be read.
 - Revised variable names (SHORT_NAME) and descriptions (LONG_NAME) to match M21C file specs.
+- Renamed tilecoord%pfaf to %pfaf_index; added matlab tile file reader.
 
 ### Fixed