Support .php-version file for version detection

[stevelacey]

---

name: 🎉 New Feature
about: Support reading PHP version from file when version is not explicitly supplied, defaults to .php-version
labels: enhancement

---

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If you're fixing a bug, adding a new feature or improving something please provide the details in discussions,
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Related discussion: #629

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Thank you for your contribution.

Description

This PR [briefly explain what it does]

In case this PR introduced TypeScript/JavaScript code changes:

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

In case this PR edits any scripts:

• I have checked the edited scripts for syntax.
• I have tested the changes in an integration test (If yes, provide workflow YAML and link).

[codecov]

Codecov Report

Merging #690 (fd03521) into develop (baf9535) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##           develop      #690   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            6         6           
  Lines          539       554   +15     
  Branches        81        85    +4     
=========================================
+ Hits           539       554   +15     

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

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[shivammathur]

@stevelacey Thanks for the contribution 🎉