Add strict typing for Breadcrumbs Visibility

Found the issues when executing phpcs

prabue@Iclusters-MacBook-Pro drupal-9 % phpcs --standard=Drupal,DrupalPractice --extensions=php,module,inc,install,test,profile,theme,css,info,txt,md,yml breadcrumbs_visibility

FILE: /Users/prabue/Desktop/Projects/drupal-9/breadcrumbs_visibility/breadcrumbs_visibility.module
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FOUND 0 ERRORS AND 2 WARNINGS AFFECTING 2 LINES
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17 | WARNING | Global constants should not be used, move it to a class or interface
174 | WARNING | #description values usually have to run through t() for translation
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FILE: /Users/prabue/Desktop/Projects/drupal-9/breadcrumbs_visibility/tests/src/FunctionalJavascript/PermissionTest.php
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FOUND 2 ERRORS AFFECTING 2 LINES
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167 | ERROR | [x] Expected 1 blank line after function; 0 found
168 | ERROR | [x] The closing brace for the class must have an empty line before it
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PHPCBF CAN FIX THE 2 MARKED SNIFF VIOLATIONS AUTOMATICALLY
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FILE: /Users/prabue/Desktop/Projects/drupal-9/breadcrumbs_visibility/README.md
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FOUND 1 ERROR AND 6 WARNINGS AFFECTING 7 LINES
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10 | WARNING | [ ] Line exceeds 80 characters; contains 298 characters
12 | WARNING | [ ] Line exceeds 80 characters; contains 87 characters
19 | WARNING | [ ] Line exceeds 80 characters; contains 164 characters
20 | WARNING | [ ] Line exceeds 80 characters; contains 115 characters
21 | WARNING | [ ] Line exceeds 80 characters; contains 216 characters
25 | WARNING | [ ] Line exceeds 80 characters; contains 265 characters
38 | ERROR | [x] Expected 1 newline at end of file; 0 found
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PHPCBF CAN FIX THE 1 MARKED SNIFF VIOLATIONS AUTOMATICALLY
------------------------------------------------------------------------------

Time: 384ms; Memory: 10MB

Found the issues when executing phpcs

Thanks, but this issue is about adding strict type checking, not coding standards.