loki/.github/pull_request_template.md

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**What this PR does / why we need it**:

**Which issue(s) this PR fixes**:
Fixes #<issue number>

**Special notes for your reviewer**:

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Note about CHANGELOG entries, if a change adds:
* an important feature
* fixes an issue present in a previous release, 
* causes a change in operation that would be useful for an operator of Loki to know
then please add a CHANGELOG entry.

For documentation changes, build changes, simple fixes etc please skip this step. We are attempting to curate a changelog of the most relevant and important changes to be easier to ingest by end users of Loki.

Note about the upgrade guide, if this changes:
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* anything to do with any API
* any other change that would require special attention or extra steps to upgrade
Please document clearly what changed AND what needs to be done in the upgrade guide.
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**Checklist**
- [ ] Documentation added
- [ ] Tests updated
- [ ] Is this an important fix or new feature? Add an entry in the `CHANGELOG.md`.
- [ ] Changes that require user attention or interaction to upgrade are documented in `docs/sources/upgrading/_index.md`