Merge pull request #2757 from martinholmer/growfactors-ctor

Revise GrowFactors constructor to handle custom growfactors files

docs/about/releases.md

@@ -3,6 +3,21 @@ Release history
 Go [here](https://github.com/PSLmodels/Tax-Calculator/pulls?q=is%3Apr+is%3Aclosed)
 for a complete commit history.
 
+2024-06-01 Release 4.0.0
+------------------------
+(last merged pull request is
+[#2752](https://github.com/PSLmodels/Tax-Calculator/pull/2752))
+
+**This is a major release with changes that make Tax-Calculator incompatible with earlier releases.**
+
+**API Changes**
+- Apply a new framework for the payroll tax policy parameters: Payroll tax parameters are split into the employer side and employee side ~ `FICA_mc_trt`, `FICA_ss_trt` are replaced by `FICA_mc_trt_employer`, `FICA_mc_trt_employee`, `FICA_ss_trt_employer` and `FICA_ss_trt_employee`. [[#2669](https://github.com/PSLmodels/Tax-Calculator/pull/2669) by Bodi Yang]
+- CDCC rate scale (`CDCC_crt`, `CDCC_frt`) changed from 0~1 to 0~100. [[#2628](https://github.com/PSLmodels/Tax-Calculator/pull/2628) by Duncan Hobbs and [#2671](https://github.com/PSLmodels/Tax-Calculator/pull/2671) by Jason DeBacker]
+
+**New Features**
+- Ablility to perform payroll tax reform upon either employer side or employee side. [by Bodi Yang]
+
+
 2024-05-10 Release 3.6.0
 ------------------------
 (last merged pull request is