Update changelog

CHANGELOG.md

+v0.5.3 - 2020-10-17
+===================
+- Add PCF8575 support. #121
+- Add MCP3008 sensor support. #115
+- Add AHT20 sensor support. #122
+- Add BME280 sensor support. #132
+- Install requirements using current Python executable. #134
+- Add sensors to HASS discovery. #133
+- Add option to publish output value on startup. #125
+
 v0.5.2 - 2020-10-17
 ===================
 - Update PyYAML to a version that doesn't suffer from CVE-2020-1747 vulnerability.