Add E-Invoicing page under Experience Middleware

[Copilot]

Adds a new E-Invoicing topic to the Experience Middleware section of the docs portal, covering the converging landscape of fiscalization and structured electronic invoicing across EU markets.

New content (e-invoicing.md)

• Terminology — eInvoice vs. eDelivery vs. eReporting; EN 16931, Peppol, XRechnung, ZUGFeRD/Factur-X, FatturaPA, CTC
• Formats vs. delivery channels — format/standard/market matrix + delivery channel table (Peppol, SDI, POS System API, etc.)
• Regulatory models — post-audit, clearance, DCTC, and eReporting with example countries
• Middleware integration — how ReceiptRequest/ReceiptResponse extends to e-invoice generation and delivery without a separate POS integration
• Country overview — DE, AT, FR, IT, PT, BE, ES: format, delivery channel, fiskaltrust roadmap status
• FAQ — addresses digital receipt vs. e-invoice distinction, integration overhead, format support

Navigation changes

• toc.js — adds e-invoicing as a top-level item under Experience Middleware (after Payment, before Digital Receipt)
• introduction.md — lists E-Invoicing as a fourth Experience component alongside Payment, Digital Receipt, and InStore App

Original prompt

Create a new documentation portal page/topic named E-Invoicing under Experience Middleware in the docs.fiskaltrust.cloud documentation portal (path: docs/poscreators/get-started). The page should be user-friendly but still useful for technical readers.

Goal

Add a new entry/page in the docs navigation and content hierarchy so users can discover and understand fiskaltrust E-Invoicing as part of Experience Middleware.

Primary source of truth

Use the content and structure from GitHub issue fiskaltrust/fiskaltrust#273 as the main source for terminology, concepts, country/format/model overview, and messaging.

Desired content characteristics

• Write in clear, approachable documentation language for product users, while preserving enough technical depth for implementers.
• Explain what E-Invoicing is, how it relates to fiscalization, and how it fits into Experience Middleware.
• Summarize the key distinctions between eInvoice, eDelivery, and eReporting.
• Provide a concise overview of formats, delivery channels, and regulatory models.
• Include a practical explanation of how POS/ERP/e-commerce systems interact with the POS System API for e-Invoices.
• Make the page consistent with the existing docs portal style and structure.

Suggested sections

• Overview / introduction
• Why this matters
• Terminology
• Formats vs delivery
• Regulatory models
• How fiskaltrust handles it in Middleware
• Supported/roadmap markets or country overview
• FAQ or next steps

Notes

• Keep the page concise enough for documentation portal consumption; do not copy the issue verbatim.
• Where appropriate, link back to the source issue for internal reference, if that fits the docs style.
• Ensure the new page is discoverable from the Experience Middleware section and is named E-Invoicing.

Acceptance criteria

• A new page/topic entry named E-Invoicing exists under Experience Middleware in the docs portal navigation.
• The page content is added and rendered correctly.
• The content is readable for both non-technical stakeholders and technical implementers.
• The page is aligned with the factual content from fiskaltrust/fiskaltrust#273.

Repository / project context

Docs portal: https://docs.fiskaltrust.cloud/docs/poscreators/get-started
Complementary source: https://github.com/fiskaltrust/fiskaltrust/issues/273

The following is the prior conversation context from the user's chat exploration (may be truncated):

User: create a new entry/topic/page named E-Invoicing to the https://docs.fiskaltrust.cloud/docs/poscreators/get-started documentation portal under Experience Middleware. The content should be user-friendly for also technical users. The other source to complement the text can be found at this GH issue: @fiskaltrust/fiskaltrust/issues/273

Assistant: I’m waiting for your response to continue.

This pull request was created from Copilot chat.