Add empty CHANGELOG.md (#257)

## Type of change

<!--Delete points that do not apply-->

- New feature

## Changes

The following changes have been made:

- Adds CHANGELOG.md file
- Adds check in PR template to ensure CHANGELOG.md file has been updated

Closes #247 

## Checklist

- [x] I have linked to any relevant issues.
- [x] I have commented my code, particularly in hard-to-understand
areas.
- [x] I have updated the documentation where relevant (API docs, the
reference, and the Sway book).
- [ ] If my change requires substantial documentation changes, I have
[requested support from the DevRel
team](https://github.com/FuelLabs/devrel-requests/issues/new/choose)
- [x] I have added tests that prove my fix is effective or that my
feature works.
- [x] I have added (or requested a maintainer to add) the necessary
`Breaking*` or `New Feature` labels where relevant.
- [x] I have done my best to ensure that my PR adheres to [the Fuel Labs
Code Review
Standards](https://github.com/FuelLabs/rfcs/blob/master/text/code-standards/external-contributors.md).
- [x] I have requested a review from the relevant team or maintainers.

.github/PULL_REQUEST_TEMPLATE.md

@@ -35,3 +35,4 @@ Closes #\<issue number\>
 - [ ] I have added (or requested a maintainer to add) the necessary `Breaking*` or `New Feature` labels where relevant.
 - [ ] I have done my best to ensure that my PR adheres to [the Fuel Labs Code Review Standards](https://github.com/FuelLabs/rfcs/blob/master/text/code-standards/external-contributors.md).
 - [ ] I have requested a review from the relevant team or maintainers.
+- [ ] I have updated the changelog to reflect the changes on this PR.

CHANGELOG.md

@@ -0,0 +1,30 @@
+# Change Log
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](http://keepachangelog.com/)
+and this project adheres to [Semantic Versioning](http://semver.org/).
+
+## [Unreleased] - yyyy-mm-dd
+
+Description of the upcoming release here.
+
+### Added
+
+- Something new here 1
+- Something new here 2
+
+### Changed
+
+- Something changed here 1
+- Something changed here 2
+
+### Fixed
+
+- Some fix here 1
+- Some fix here 2
+
+#### Breaking
+
+- Some breaking change here 1
+- Some breaking change here 2