changelog: Add entry about evmc-vmtester's CMake helper
## [6.3.0] - unreleased
+- Added: [[#303](https://github.com/ethereum/evmc/pull/303)]
+ A CMake helper for running evmc-vmtester.
- Added: [[#313](https://github.com/ethereum/evmc/pull/313)]
The loader module introduces standardized EVMC module configuration string
which contains path to the module and additional options.
