Update doc on Community target build and release procedures.

Signed-off-by: José Simões <jose.simoes@eclo.solutions>

docs/maintainers/community-targets-build-release.md

@@ -36,3 +36,6 @@ Community target images are distributed through **nanoFramework** JFrog Bintray
 When merging a PR make sure to add to the commit message the token(s) for the targets to build, otherwise the merge to the master branch won't trigger a build for any board.
 
 It's possible to manually start a build _and_ specify that it should build all targets. This is most handy, for example, after a number of changes in the nf-interpreter repo to build new images for the Community targets. Another situation is when one forgets to add the build token in the PR merge and needs to trigger a build afterwards.
+
+To do this, go to the Builds page in the project Azure Pipelines and hit the 'Queue' button. When the pop-up shows, change the BUILD_ALL variable to 'true'. Like this:
+![](../images/docs-trigger-build-all-community-targets.png)