feat: add gross prices

[Lewa-Reka]

close #13

[github-actions]

✅⚠️MegaLinter analysis: Success with warnings

Descriptor	Linter	Files	Fixed	Errors	Warnings	Elapsed time
✅ ACTION	actionlint	4		0	0	0.2s
✅ JSON	jsonlint	5		0	0	0.58s
⚠️ JSON	prettier	5		1	0	0.65s
✅ JSON	v8r	5		0	0	3.56s
✅ MARKDOWN	markdownlint	8		0	0	0.89s
⚠️ MARKDOWN	markdown-table-formatter	8		1	0	0.27s
✅ PYTHON	bandit	37		0	0	4.68s
✅ PYTHON	pyright	37		0	0	6.38s
✅ PYTHON	ruff	37		0	0	0.02s
✅ REPOSITORY	checkov	yes		no	no	19.82s
✅ REPOSITORY	gitleaks	yes		no	no	0.35s
✅ REPOSITORY	git_diff	yes		no	no	0.01s
✅ REPOSITORY	grype	yes		no	no	38.0s
✅ REPOSITORY	secretlint	yes		no	no	1.12s
✅ REPOSITORY	syft	yes		no	no	2.07s
✅ REPOSITORY	trivy	yes		no	no	10.88s
✅ REPOSITORY	trivy-sbom	yes		no	no	0.16s
✅ REPOSITORY	trufflehog	yes		no	no	4.16s
✅ SPELL	lychee	25		0	0	1.12s
✅ YAML	prettier	11		0	0	0.68s
✅ YAML	v8r	11		0	0	8.54s
✅ YAML	yamllint	11		0	0	0.6s

Detailed Issues

⚠️ MARKDOWN / markdown-table-formatter - 1 error

1 files contain markdown tables to format:
- docs/MIGRACJA-V2.md

⚠️ JSON / prettier - 1 error

Checking formatting...
[warn] custom_components/rce_pse/translations/en.json
[warn] custom_components/rce_pse/translations/pl.json
[warn] Code style issues found in 2 files. Run Prettier with --write to fix.

See detailed reports in MegaLinter artifacts