Construct the HTML page title inside the AbstractPage class

[caendesilva]

This provides a canonical place to assemble the displayed page title, while also making it easier to customize from the backend in the future.

[codecov]

Codecov Report

Merging #294 (0b02c7f) into master (6956bda) will not change coverage.
The diff coverage is 100.00%.

❗ Current head 0b02c7f differs from pull request most recent head eee9001. Consider uploading reports for the commit eee9001 to get more accurate results

@@             Coverage Diff             @@
##              master      #294   +/-   ##
===========================================
  Coverage     100.00%   100.00%           
- Complexity       813       815    +2     
===========================================
  Files             96        96           
  Lines           2033      2038    +5     
===========================================
+ Hits            2033      2038    +5     

Impacted Files	Coverage Δ
packages/framework/src/Contracts/AbstractPage.php	100.00% <100.00%> (ø)

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