Release v0.9.9 (#1799)

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

**Which issue(s) this PR fixes**:

Fixes #

**Does this PR introduce a user-facing change?**:
<!--
If no, just write "NONE" in the release-note block below.
-->
```release-note
NONE
```

This PR was merged by Kapetanios.

docs/content/en/blog/releases/v0.9.9.md

@@ -0,0 +1,25 @@
+---
+title: "Release v0.9.9"
+linkTitle: "Release v0.9.9"
+date: 2021-03-30
+description: >
+  Release v0.9.9
+---
+
+## Changelog since v0.9.8
+
+### Notable Changes
+* Re-enable supporting MongoDB ([#1794](https://github.com/pipe-cd/pipe/pull/1794))
+* Add a new configuration field for the ANALYSIS stage named "skipOnNoData" which can control how to handle no data case. ([#1771](https://github.com/pipe-cd/pipe/pull/1771))
+
+### Internal Changes
+* Add build cache for building play image ([#1797](https://github.com/pipe-cd/pipe/pull/1797))
+* Add MongoDB configuration docs ([#1796](https://github.com/pipe-cd/pipe/pull/1796))
+* Add playground build job to the CI ([#1793](https://github.com/pipe-cd/pipe/pull/1793))
+* Add an util method to the web test utils ([#1791](https://github.com/pipe-cd/pipe/pull/1791))
+* Add UpdateServicePrimaryTaskSet to ECS deployment ([#1784](https://github.com/pipe-cd/pipe/pull/1784))
+* Refactor deployment config form ([#1787](https://github.com/pipe-cd/pipe/pull/1787))
+* Handle cancel signal in case it came on the previous stage ([#1790](https://github.com/pipe-cd/pipe/pull/1790))
+* Fix error format on print rollback error message ([#1789](https://github.com/pipe-cd/pipe/pull/1789))
+* Update CI config for web testing ([#1788](https://github.com/pipe-cd/pipe/pull/1788))
+* Update web test config ([#1783](https://github.com/pipe-cd/pipe/pull/1783))

release/RELEASE

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-version: v0.9.8
+version: v0.9.9