Initial changelog

Also simple process/script to manage entries in PR's without merge conflicts:

1. Unreleased entries area stored as text files in ".changelogs/"
2. On release these are concatenated together and put in CHANGELOG.md

Script basically just add line of text to a "YYYY-MM-DD-branch.txt" formatted file

CHANGELOG.md

@@ -0,0 +1,20 @@
+# Changelog
+
+## [Unreleased]
+
+Note: unreleased change log entries are kept in `.changelogs/` directory in repo root, and can be added with `./script/changelog.py add "Added thing for reason"
+
+## 0.3.0 - 2021-01-11
+- Flexible named reports
+- Updates to the TaskChampion crate API
+- Usability improvements
+
+## 0.2.0 - 2020-11-30
+
+This release is the first "MVP" version of this tool. It can do basic task operations, and supports a synchronization. Major missing features are captured in issues, but briefly:
+
+    better command-line API, similar to TaskWarrior
+    authentication of the replica / server protocol
+    encryption of replica data before transmission to the server
+    lots of task features (tags, annotations, dependencies, ..)
+    lots of CLI features (filtering, modifying, ..)