Update maxking/mailman-core Docker tag to v0.5

This MR contains the following updates:

Package	Update	Change
maxking/mailman-core	minor	0.4 -> 0.5

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This MR has been generated by Renovate Bot.

restored source branch renovate/templates-maxking-mailman-core-0.x

mentioned in issue #40

changed the description

added 63 commits

• d70f9594...cb907c40 - 62 commits from branch master
• 3c60655e - Update maxking/mailman-core Docker tag to v0.5

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