Feat: Change siteId to a String type

[jainhitesh9998]

Describe the bug
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Configuring Matomo-ProtectTrackID enables us to use hash instead of int as part of site-id.
Changing the datatype of siteid from in to String has no affect on the functionality, but improves the compatibility with the ProtectTrackID library as the site id generated then are string.

To Reproduce
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2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior
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Screenshots
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Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context
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[jainhitesh9998]

we have tested it with our setup, can raise a PR for the same.

[TesteurManiak]

Sure! I don't see any problem with changing MatomoTracker.siteId to a String type. You can open a PR for review, otherwise I'll make the changes after my vacations.

[ken717w]

Just upgraded from 4.x to 5.0 and found this breaking change. This should be mentioned in the upgrade guide.

[TesteurManiak]

@ken717w Documentation has been updated