Add v1.2.0 changelog

CHANGELOG.md

+## [v1.2.0](https://git.duniter.org/clients/python/duniterpy/-/milestones/20) (31st January 2024)
+
+### Code
+
+- #201, !181, !184: Support BMA changes
+- #203, !185: Store authentication files only as user readable
+- #88, !186: WS2P head: Use dataclasses in place of `attrs`
+- #200, !189: Define custom exceptions to support new Pylint v2.16 rule: `broad-exception-raised`
+- !193: Raise exception when no password is passed with EWIF format
+
+### DevEnv
+
+- #202, !183: Introduce `pre-commit-hooks`
+- #205, !195: Fix `gitlab-ci-lint` hook
+- #195, !175: Add coverage integration into GitLab
+
+### Meta
+
+- !175, !182: Bump rte and dev dependencies
+  - !178: Support Mypy v1.4.0
+  - #204, !187: `jsonchema` bump to v4 (`2020-12` draft) breaks `bma.blockchain.difficulties`
+- !190: Support libnacl v1.9.0 onward
+- #196, !180: Add support for Python v3.12
+- #194, !176: Add support for Python v3.11
+- #193, !179: Drop Python v3.7 support
+- #192, !177: Bump copyright to 2023
+- #197, !196: Bump copyright to 2024
+
+### Documentation
+
+- #105, #155, !188: Clarify `README.md` and `CONTRIBUTING.md` documentation
+
+______________________________________________________________________
+
+- Thanks @Moul, @vtexier
+
 ## v1.1.1 (14th August 2023)
 
 Bug fix release, because `libnacl` brought in a breaking change.