Add dependabot update hint to README.md

Dependabot PRs are much easier to merge than custom PRs (don’t need a
separate second reviewer), so here’s how to create more of them. This
somewhat contradicts the previous paragraphs about grouping commits
together, but in my experience during recent chores, there are quite
many outdated packages that don’t really need to be grouped with
anything else, and where merging the dependabot PR is actually fine.

Bug: T350664

README.md

@@ -133,6 +133,11 @@ For example, this can be one commit for each of:
 
 Make sure that all checks still pass for every commit.
 
+If you’re working with dependabot,
+and it ran into the limit of open pull requests or its PRs are otherwise outdated,
+you can trigger a new run at
+[Insights > Dependency graph > Dependabot](https://github.com/wmde/new-lexeme-special-page/network/updates) > Recent update jobs > Check for updates.
+
 Once all dependency updates are merged, update the submodule version in WikibaseLexeme (see below).
 
 ## Updating the submodule version in WikibaseLexeme