feat: Add LinksTo Property

[octfx]

This PR adds a new Links to property that records pages to which a page links.

The namespaces where this property is allowed to be active can be configured using $sespgLinksToEnabledNamespaces.

Example:
$sespgLinksToEnabledNamespaces = [ 10, 838 ]; would activate the Links to property only on Template and Module namespaces.

This PR includes:

• Tests (unit)
• CI build passed

[codecov-commenter]

Codecov Report

Merging #216 (3fc38c6) into master (b5af401) will decrease coverage by 1.24%.
The diff coverage is 54.28%.

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@@             Coverage Diff              @@
##             master     #216      +/-   ##
============================================
- Coverage     91.42%   90.19%   -1.24%     
- Complexity      357      368      +11     
============================================
  Files            35       36       +1     
  Lines          1015     1050      +35     
============================================
+ Hits            928      947      +19     
- Misses           87      103      +16     

Impacted Files	Coverage Δ
...rc/PropertyAnnotators/LinksToPropertyAnnotator.php	54.28% <54.28%> (ø)

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