Feat: add dependency importing from Maven Central

[wilyJ80]

Good job, I think this is pretty close to being a perfect tool for Java developers who want to work within the Neovim editor. But there's one thing that's missing to make it 100% perfect for 99% of the people: searching and adding a dependency from Maven Central to the pom.xml. VSCode's Maven plugin does it and it's just great, but I can't figure out how to do it :cry: Here's the plugin, in case you want to try this feature sometime: https://github.com/microsoft/vscode-maven