Interactive visualization of requirements graphs in html with pyvis

[MathisFederico]

Add a better interactive visualization of requirements graphs in html with pyvis.

Still missing an update on the layer layout to avoid superposition in recursive environments.

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
✅ -0.76% (target: -1.00%)	∅

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (2a0be5c)	3551	3343	94.14%
Head commit (ded3908)	3671 (+120)	3428 (+85)	93.38% (-0.76%)

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 (#38)	0	0	∅ (not applicable)

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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_{You may notice some variations in coverage metrics with the latest Coverage engine update. For more details, visit the documentation}