DrupalBootstrapStyles: Inverted filter logic causes duplicate CSS files

Problem/Motivation

I believe a regression bug was introduced in the DrupalBootstrapStyles provider class. The conversion of strpos() !== 0 to str_contains() in the parseAssets() method inverted the filtering logic, causing the following behaviour in my case:

<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/entreprise7pro-bootstrap@3.4.8/dist/css/bootstrap.css" />
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@unicorn-fail/drupal-bootstrap-styles@0.0.2/dist/3.1.1/7.x-3.x/drupal-bootstrap.css" />
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@unicorn-fail/drupal-bootstrap-styles@0.0.2/dist/3.1.1/8.x-3.x/drupal-bootstrap.css" />
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@unicorn-fail/drupal-bootstrap-styles@0.0.2/dist/3.2.0/7.x-3.x/drupal-bootstrap.css" />
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@unicorn-fail/drupal-bootstrap-styles@0.0.2/dist/3.2.0/8.x-3.x/drupal-bootstrap.css" />
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@unicorn-fail/drupal-bootstrap-styles@0.0.2/dist/3.3.1/7.x-3.x/drupal-bootstrap.css" />

I believe the logic is inverted: strpos() !== 0 checks if the string starts at position 0, while str_contains() checks if the string contains the pattern anywhere. The correct PHP 8+ conversion should use str_starts_with().

On top of that, there is no drupal-bootstrap.css loaded for newer Bootstrap versions (3.4.2-3.4.8) so if I understand correctly, we need to map these versions to the latest available version (3.4.1)

Steps to reproduce

1. Install version 8.x-3.38 of this theme
2. Configure jsDelivr as CDN
3. Configure version 3.4.8
4. View the HTML source of any page
5. Observe multiple duplicate drupal-bootstrap.css files being loaded from different versions and branches

Proposed resolution

1. Fix the inverted logic: change str_contains() to !str_starts_with()
2. Add mapVersion() method to map Bootstrap 3.4.2-3.4.8 to available version 3.4.1 (following the pattern in Bootstrap::glyphicons())

Remaining tasks

• Review and test patch
• Commit fix

User interface changes

None.

API changes

None. Restores original intended behavior.

Data model changes

None.