[doc]: Added branch 201904 to the build status icons (#3642)

Somehow this was missed in april, I added the icons for 201904 so that
the branch is not forgotten

Signed-off-by: Michel Moriniaux <m.moriniaux@criteo.com>

README.md

@@ -6,6 +6,15 @@ Nephos: [![Nephos](https://sonic-jenkins.westus2.cloudapp.azure.com/job/nephos/j
 P4: [![P4](https://sonic-jenkins.westus2.cloudapp.azure.com/job/p4/job/buildimage-p4-all/badge/icon)](https://sonic-jenkins.westus2.cloudapp.azure.com/job/p4/job/buildimage-p4-all)
 VS: [![VS](https://sonic-jenkins.westus2.cloudapp.azure.com/job/vs/job/buildimage-vs-all/badge/icon)](https://sonic-jenkins.westus2.cloudapp.azure.com/job/vs/job/buildimage-vs-all)
 
+*201904*:
+Broadcom: [![Broadcom](https://sonic-jenkins.westus2.cloudapp.azure.com/job/broadcom/job/buildimage-brcm-201904/badge/icon)](https://sonic-jenkins.westus2.cloudapp.azure.com/job/broadcom/job/buildimage-brcm-201904/)
+Barefoot: [![Mellanox](https://sonic-jenkins.westus2.cloudapp.azure.com/job/barefoot/job/buildimage-bf-201904/badge/icon)](https://sonic-jenkins.westus2.cloudapp.azure.com/job/barefoot/job/buildimage-bf-201904/)
+Centec: [![Centec](https://sonic-jenkins.westus2.cloudapp.azure.com/job/centec/job/buildimage-centec-201904/badge/icon)](https://sonic-jenkins.westus2.cloudapp.azure.com/job/centec/job/buildimage-centec-201904/)
+Nephos: [![Nephos](https://sonic-jenkins.westus2.cloudapp.azure.com/job/nephos/job/buildimage-nephos-201904/badge/icon)](https://sonic-jenkins.westus2.cloudapp.azure.com/job/nephos/job/buildimage-nephos-201904/)
+Marvell: [![Marvell](https://sonic-jenkins.westus2.cloudapp.azure.com/job/marvell/job/buildimage-mrvl-201904/badge/icon)](https://sonic-jenkins.westus2.cloudapp.azure.com/job/marvell/job/buildimage-mrvl-201904/)
+Mellanox: [![Mellanox](https://sonic-jenkins.westus2.cloudapp.azure.com/job/mellanox/job/buildimage-mlnx-201904/badge/icon)](https://sonic-jenkins.westus2.cloudapp.azure.com/job/mellanox/job/buildimage-mlnx-201904/)
+VS: [![VS](https://sonic-jenkins.westus2.cloudapp.azure.com/job/vs/job/buildimage-vs-201904/badge/icon)](https://sonic-jenkins.westus2.cloudapp.azure.com/job/vs/job/buildimage-vs-201904)
+
 *201811*:
 Broadcom: [![Broadcom](https://sonic-jenkins.westus2.cloudapp.azure.com/job/broadcom/job/buildimage-brcm-201811/badge/icon)](https://sonic-jenkins.westus2.cloudapp.azure.com/job/broadcom/job/buildimage-brcm-201811/)
 Barefoot: [![Mellanox](https://sonic-jenkins.westus2.cloudapp.azure.com/job/barefoot/job/buildimage-bf-201811/badge/icon)](https://sonic-jenkins.westus2.cloudapp.azure.com/job/barefoot/job/buildimage-bf-201811/)