Add dependabot.yml for dependency version updates

[kanwalpreetd]

What

Adding base config for dependabot.yml, which enables automatic PRs for dependency version updates through Dependabot. This base config sets version updates to run on a weekly schedule, groups PRs for version updates, and sets max PRs that Dependabot can create for version updates per package-ecosystem.
But if you would like, several config options can be added to dependabot.yml as per configuration-options-for-the-dependabot.yml-file to customize version updates, such as:

• Group PRs for version updates by different criteria
• Set reviewers for Dependabot version updates PRs
• Etc.

Also, automatic PRs for security updates through Dependabot are already enabled through a global setting. PRs for security updates will be grouped as much as possible across directories and per ecosystem through the global setting (grouping-dependabot-security-updates). But dependabot.yml can also be used for more granular security updates settings in addition to version updates (some of the options in dependabot.yml are shared across security and version updates), such as:

• Grouping security updates according to custom criteria: overriding-the-default-behavior-with-a-configuration-file
• Etc.

Why

To enable using the latest package versions, and provide a way to customize Dependabot security updates PRs.

Known limitations

N/A

[Ifropc]

Thanks for this PR @kanwalpreetd !
In this project and anchor platform we are using gradle/libs.versions.toml file to store dependencies and their versions. Do you know if dependabot supports this structure?

[kanwalpreetd]

@Ifropc I think I checked when creating this PR, don't think it picked up gradle/libs.versions.toml. But I will check again shortly.

[kanwalpreetd]

@Ifropc It should work now for gradle/libs.versions.toml too (there was an issue with the path when I tried earlier, it wanted me to reference the base dir even though the file is under gradle/, usually that's not the case for other build systems)

[Ifropc]

Thanks @kanwalpreetd let's try merging it and see how it works

[kanwalpreetd]

thanks, looks like it's working as intended. (as mentioned above, feel free to adjust the config further through: configuration-options-for-the-dependabot.yml-file)