Validating from version - changelog (#790)

* Adding fromversion check in validate

* Adding fromversion check in validate

* Update TestSuite/assets/default_script/sample_script.yml

Co-authored-by: Bar Katzir <37335599+bakatzir@users.noreply.github.com>

* Update demisto_sdk/commands/common/hook_validations/content_entity_validator.py

Co-authored-by: Bar Katzir <37335599+bakatzir@users.noreply.github.com>

* adding doc string

* skipping reputations json

* adding changelog

* adding changelog

Co-authored-by: Bar Katzir <37335599+bakatzir@users.noreply.github.com>

CHANGELOG.md

@@ -27,7 +27,8 @@
 * Added support for *prev-ver* flag in **lint** and **secrets** commands.
 * Added support for *text* flag to **update-release-notes** command to add the same text to all release notes.
 * Fixed an issue where **validate** did not recognize added files if they were modified locally.
-* Added a validation to the **validate** command that checks that the certification field in the pack_metadata file is valid.
+* Added a validation that checks the `fromversion` field exists and is set to 5.0.0 or above when working or comparing to a non-feature branch in **validate** command.
+* Added a validation that checks the certification field in the pack_metadata file is valid in **validate** command.
 
 # 1.2.1
 * Added an additional linter `XSOAR-linter` to the **lint** command which custom validates py files. currently checks for: