Update CHANGELOG.md with latest changes and additions

CHANGELOG.md

+### v0.2.3 ###
+**Virtual Sensing**\
+\+ Added function to estimate the observation filters in the time-domain.\
+\+ Added function to perform estimation with observation filters in the time-domain.
+
+**Signal Processing - Generic**\
+\* Fixed bugs, improved calculations and removed output arguments for the windowed sinc FIR fractional delay filters
+\+ Added four window functions in the calculation of windowed sinc FIR fractional delay filters.\
+
+
+### v0.2.2 ###
+**Virtual Sensing**\
+\* Update the observation filter and estimation with observation filter functions with better input argument checking and changed the name of variables to match those in the literature.
+
+
 ### v0.2.1 ###
 **Virtual Sensing**\
 \* Fix a bug where noise was added to the power spectral density matrix for the optimal observation filter calculations in the noiseless case.