docs: Add comment/changelog about not including guest twice

CHANGELOG.md

@@ -13,6 +13,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - [#637](https://github.com/ClementTsang/bottom/pull/637): Fix process CPU calculation if /proc/stat CPU line has less values than expected
 
+## Changes
+
+- [#637](https://github.com/ClementTsang/bottom/pull/637): Remove duplicate guest time in process CPU calculation
+
 ## [0.6.5] - 2021-12-19
 
 ## Bug Fixes

src/app/data_harvester/processes/linux.rs

@@ -53,6 +53,7 @@ fn calculate_idle_values(line: String) -> (f64, f64) {
     let steal: f64 = str_to_f64(val.next());
 
     // Note we do not get guest/guest_nice, as they are calculated as part of user/nice respectively
+    // See https://github.com/htop-dev/htop/blob/main/linux/LinuxProcessList.c
 
     let idle = idle + iowait;
     let non_idle = user + nice + system + irq + softirq + steal;