feat: add functionality to keep custom intellij modules

[ARau87]

As described in #589 intellij modules are overwritten at each melos bootstrap. The reason for this is that the whole modules.xml file isrecreated at every bootstrap.

Closes #589

Description

• Added xml dependency to read and parse the xml content of the modules.xml properly
• Added a function to compare the modules inside the current modules.xml with the melos modules. Then merge them before recreating the modules.xml.

Type of Change

• ✨ feat -- New feature (non-breaking change which adds functionality)
• 🛠️ fix -- Bug fix (non-breaking change which fixes an issue)
• ❌ ! -- Breaking change (fix or feature that would cause existing functionality to change)
• 🧹 refactor -- Code refactor
• ✅ ci -- Build configuration change
• 📝 docs -- Documentation
• 🗑️ chore -- Chore

[docs-page]

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docs.page/invertase/melos~949

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[spydon]

@ARau87 can you have a look at the analyze issues?

[spydon]

Thanks for your contribution!