chore: update CONTRIBUTION.md to include change files section

CONTRIBUTING.md

@@ -39,6 +39,53 @@ To send us a pull request, please:
 GitHub provides additional document on [forking a repository](https://help.github.com/articles/fork-a-repo/) and 
 [creating a pull request](https://help.github.com/articles/creating-a-pull-request/).
 
+## Adding a `change file` to your contribution branch
+
+Each contribution branch should include a `change file` that contains a changelog message for each project that has been updated, as well as the type of increment to perform for those changes when versioning the project.
+
+A `change file` looks like the following example:
+```json
+{
+ "Projects": [
+ {
+ "Name": "AWS.Logger.Core",
+ "Type": "Patch",
+ "ChangelogMessages": [
+ "Fixed an issue causing a failure somewhere"
+ ]
+ }
+ ]
+}
+```
+The `change file` lists all the modified projects, the changelog message for each project as well as the increment type. 
+
+These files are located in the repo at .autover/changes/
+
+You can use the `AutoVer` tool to create the change file. You can install it using the following command:
+```
+dotnet tool install -g AutoVer
+```
+
+You can create the `change file` using the following command:
+```
+autover change --project-name "AWS.Logger.Core" -m "Fixed an issue causing a failure somewhere
+```
+Note: Make sure to run the command from the root of the repository.
+
+You can update the command to specify which project you are updating.
+The available projects are:
+* AWS.Logger.AspNetCore
+* AWS.Logger.Core
+* AWS.Logger.Log4net
+* AWS.Logger.SeriLog
+* NLog.AWS.Logger
+
+The possible increment types are:
+* Patch
+* Minor
+* Major
+
+Note: You do not need to create a new `change file` for every changelog message or project within your branch. You can create one `change file` that contains all the modified projects and the changelog messages.
 
 ## Finding contributions to work on
 Looking at the existing issues is a great way to find something to contribute on. As our projects, by default, use the default GitHub issue labels ((enhancement/bug/duplicate/help wanted/invalid/question/wontfix), looking at any ['help wanted'](https://github.com/aws/aws-logging-dotnet/labels/help%20wanted) issues is a great place to start.