feat: Import formula report in report module init file

Author: gfieni

powerapi/report/__init__.py

@@ -31,4 +31,5 @@
 
 from powerapi.report.report import Report, DeserializationFail
 from powerapi.report.power_report import PowerReport
+from powerapi.report.formula_report import FormulaReport
 from powerapi.report.hwpc_report import *