add introduction to HGHC

[JoeZZG]

This pull request is about the introduction in HGHC follows the standardized template from issue #4437.

The new introduction of HGHC is:

**Introduction**
Heat transfer through the cladding of a nuclear fuel element influences performance and safety. Engineers therefore rely on dependable calculations of the heat transfer coefficients used for simulating the temperature. This document describes the requirements of a program called HGHC.

The following section provides an overview of the Software Requirements Specification (SRS) for HGHC. This section explains the purpose of this document, the scope of the requirements, the characteristics of the intended reader, and the organization of the document.

Implementation

1. Added Introduction Section to Body.hs.
2. Changed cn "HGHC" to pn "HGHC" to fix double period issue in MetaConcepts.hs

Current HGHC settings context: Heat transfer through nuclear fuel cladding progName: pn "HGHC" with abbreviation "HGHC" → auto-detects NO short form display hasProvenance: False (no external reference)

Code Reuse (Control parameters) Copy introPara, programNameWithShortForm, hasDistinctShortForm, and provenanceInfo to other examples, replace the context (i.e. introPara) with the background, and add provenanceRef information accordantly.