Closes #40: 3.19 Preload fonts beacon processing part

[jeawhanlee]

Description

Closes wp-media/wp-rocket#7241
Closes wp-media/wp-rocket#7270

Adds new script to the beacon to extract fonts used above the fold.

Type of change

• New feature (non-breaking change which adds functionality).

Detailed scenario

N/A

Technical description

Documentation

The BeaconPreloadFonts class analyzes font usage on a webpage, focusing on fonts visible above the fold. It detects network-loaded and stylesheet fonts, checks for system fonts, and verifies element visibility. The class cleans URLs, extracts @font-face rules, and summarizes font usage data, including counts of elements using each font. It logs results and handles errors during processing. Overall, it helps optimize font loading for better user experience.

New dependencies

N/A

Risks

List possible performance & security issues or risks, and explain how they have been mitigated.
See here

Mandatory Checklist

Code validation

• I validated all the Acceptance Criteria. If possible, provide screenshots or videos.
• I triggered all changed lines of code at least once without new errors/warnings/notices.
• I implemented built-in tests to cover the new/changed code.

Code style

• I wrote a self-explanatory code about what it does.
• I protected entry points against unexpected inputs.
• I did not introduce unnecessary complexity.
• Output messages (errors, notices, logs) are explicit enough for users to understand the issue and are actionnable.

Unticked items justification

N/A

Additional Checks

• In the case of complex code, I wrote comments to explain it.
• When possible, I prepared ways to observe the implemented system (logs, data, etc.).
• I added error handling logic when using functions that could throw errors (HTTP/API request, filesystem, etc.)

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
✅ +4.74% (target: -1.00%)	✅ 79.70% (target: 50.00%)

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (1e2e9c7)	677	466	68.83%
Head commit (862ae55)	1207 (+530)	888 (+422)	73.57% (+4.74%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#42)	537	428	79.70%

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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[jeawhanlee]

Some codacy issues to fix but can be reviewed now.