Addition of the release notes for v12.0.6

Signed-off-by: Florent Poinsard <florent.poinsard@outlook.fr>

doc/releasenotes/12_0_6_changelog.md

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+# Changelog of Vitess v12.0.6
+
+### Bug fixes
+#### Query Serving
+* Fix AST copying of basic types in release-12.0 [#11053](https://github.com/vitessio/vitess/pull/11053)
+* fix: return when instructions are nil in checkThatPlanIsValid [#11070](https://github.com/vitessio/vitess/pull/11070)
+#### VReplication
+* VStreamer: recompute table plan if a new table is encountered for the same id [#9978](https://github.com/vitessio/vitess/pull/9978)
+* VStream API: Fix vtgate memory leaks when context gets cancelled [#10571](https://github.com/vitessio/vitess/pull/10571)
+* VStream API: Fix vtgate memory leaks when context gets cancelled [#10923](https://github.com/vitessio/vitess/pull/10923)
+### CI/Build
+#### Build/CI
+* Fix mariadb102 and mariadb103 tests on release-12.0 [#11025](https://github.com/vitessio/vitess/pull/11025)
+* Remove MariaDB 10.2 test from release-12.0 [#11074](https://github.com/vitessio/vitess/pull/11074)
+### Enhancement
+#### General
+* Upgrade go version to `1.17.13` on `release-12.0` [#11129](https://github.com/vitessio/vitess/pull/11129)
+### Release
+#### Documentation
+* Addition of the release summary for `v12.0.6` [#11140](https://github.com/vitessio/vitess/pull/11140)
+#### General
+* Release `v12.0.5` [#10872](https://github.com/vitessio/vitess/pull/10872)
+* Include the compose examples in the `do_release` script [#11130](https://github.com/vitessio/vitess/pull/11130)

doc/releasenotes/12_0_6_release_notes.md

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+# Release of Vitess v12.0.6
+## Major Changes
+
+### Upgrade to `go1.17.13`
+
+Vitess `v12.0.6` now runs on `go1.17.13`.
+The patch release of Go, `go1.17.13`, was the main reason for this release as it includes important security fixes to packages used by Vitess.
+Below is a summary of this patch release. You can learn more [here](https://go.dev/doc/devel/release#go1.17).
+
+> go1.17.13 (released 2022-08-01) includes security fixes to the encoding/gob and math/big packages, as well as bug fixes to the compiler and the runtime.
+### End of life of MariadDB 10.2
+
+Since the end-of-life of MariaDB 10.2, its Docker image is unavailable, and we decided to remove the unit tests using this version of MariaDB. The Pull Request doing this change is available [here](https://github.com/vitessio/vitess/pull/11074).
+This change is documented on our website [here](https://vitess.io/docs/12.0/overview/supported-databases/#mariadb-versions-100-to-103).
+
+
+------------
+The entire changelog for this release can be found [here](https://github.com/vitessio/vitess/blob/main/doc/releasenotes/12_0_6_changelog.md).
+
+The release includes 11 commits (excluding merges)
+
+Thanks to all our contributors: @GuptaManan100, @dbussink, @deepthi, @frouioui, @harshit-gangal, @rohit-nayak-ps

doc/releasenotes/12_0_6_summary.md

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+## Major Changes
+
+### Upgrade to `go1.17.13`
+
+Vitess `v12.0.6` now runs on `go1.17.13`.
+The patch release of Go, `go1.17.13`, was the main reason for this release as it includes important security fixes to packages used by Vitess.
+Below is a summary of this patch release. You can learn more [here](https://go.dev/doc/devel/release#go1.17).
+
+> go1.17.13 (released 2022-08-01) includes security fixes to the encoding/gob and math/big packages, as well as bug fixes to the compiler and the runtime.
+### End of life of MariadDB 10.2
+
+Since the end-of-life of MariaDB 10.2, its Docker image is unavailable, and we decided to remove the unit tests using this version of MariaDB. The Pull Request doing this change is available [here](https://github.com/vitessio/vitess/pull/11074).
+This change is documented on our website [here](https://vitess.io/docs/12.0/overview/supported-databases/#mariadb-versions-100-to-103).