Add automatic detection of required PHP version from Composer's platform setting

[jasongill]

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name: ⚙ Improvement about: Supports automatic detection of PHP version from composer.lock or composer.json file labels: enhancement

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This is related to #751 and should help with #629, #713, and #639.

Description

This PR adds detection of the "config.platform.php" setting available in composer.json (which is also saved as platform-overrides.php in composer.lock), so that the required PHP version for an application using Composer will be automatically detected.

As the config.platform.php setting forces Composer to lock dependencies to a specific PHP version, it's a perfect way to detect the "required" version of PHP for a project without any risk of conflicts due to differing versions.

In case this PR introduced TypeScript/JavaScript code changes:

• [x] I have written test cases for the changes in this pull request
• [x] I have run npm run format before the commit.
• [x] I have run npm run lint before the commit.
• [x] I have run npm run release before the commit.
• [x] npm test returns with no unit test errors and all code covered.

[codecov[bot]]

Codecov Report

Merging #754 (95916a7) into develop (72ae4cc) will not change coverage. The diff coverage is 100.00%.

@@            Coverage Diff            @@
##           develop      #754   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            7         7           
  Lines          577       589   +12     
  Branches        92        98    +6     
=========================================
+ Hits           577       589   +12     

Files Changed	Coverage Δ
src/utils.ts	100.00% <100.00%> (ø)