Ported/Converted NativeCoreAPIReference_en_r13.pdf file from PDF to Markdown

[thynetruly]

Hello! I emailed the Live2D team last year about my comment translation script since I had successfully used it to translate the comments throughout the Live2D Cubism SDK for Native files into English for my team's internal use. Hope this can help the Live2D developer community by increasing accessibility to the API documentation! Please let me know if there are any changes, proofreading, or editing needed since I retained the original file's grammar. I tried very hard to treat this as a reference document with all of the information from the source PDF file properly reflected. I'm also willing to port the Japanese PDF, so please let me know if you need that.

[Copilot]

Pull Request Overview

This PR converts the Live2D Cubism Core API Reference from PDF format to Markdown, making the documentation more accessible to developers. The conversion includes all content from the original PDF with proper formatting, code snippets, and internal navigation links.

• Converted the entire NativeCoreAPIReference_en_r13.pdf to Markdown format
• Maintained all original content including changelog, API descriptions, and code examples
• Added proper Markdown formatting for tables, code blocks, and navigation links

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

[Copilot]

Variable name inconsistency: 'partParentIndex' is used here but 'parentPartIndices' is declared on line 738. This should be 'parentPartIndices[i]' to match the declared variable.

Suggested change

	// If partParentIndex = -1, parent is empty.
	// If partParentIndex >= 0, the value of parentPartIndices is the Index of the parent.
	for (int i = 0; i < partCount; ++i)
	{
	if(partParentIndex[i] == -1)
	{
	printf("partParentIndex[%d]:%s does not have a parent part.", i, partIds[i]);
	}
	else
	{
	printf("partParentIndex[%d]:Parent part of %s is %s.", i, partIds[i], partIds[parentPartIndices[i]]);
	// If parentPartIndices[i] = -1, parent is empty.
	// If parentPartIndices[i] >= 0, the value of parentPartIndices is the Index of the parent.
	for (int i = 0; i < partCount; ++i)
	{
	if(parentPartIndices[i] == -1)
	{
	printf("parentPartIndices[%d]:%s does not have a parent part.", i, partIds[i]);
	}
	else
	{
	printf("parentPartIndices[%d]:Parent part of %s is %s.", i, partIds[i], partIds[parentPartIndices[i]]);

[thynetruly]

Here is the original code from the PDF document for reference. The lines with the potential discrepancy/inconsistency are 4 onward:

// Getting the ID list of parts.
const char** partIds =csmGetPartIds(model);
// Getting the parent of the index list of parts.
const int* parentPartIndices =csmGetPartParentPartIndices(model);
// If partParentIndex = -1, parent is empty.
// If partParentIndex> = 0, the value of parentPartIndices is the Index of the parent.
for (int i = 0; i < partCount; ++i)
{
if(partParentIndex[i] == -1)
{
printf("partParentIndex[%d]:%s does not have a parent part.
"
,i,partIds[i]);
}
{
else
printf("partParentIndex[%d]:Parent part of %s is %s.
"
,i,partIds[i],partIds[parentPartIndices[i]]);
}
}