feat: add PPTX editing and creation skills with comprehensive documentation

- Introduced new skills for editing and creating PPTX presentations, including a detailed guide on template-based workflows and script usage.
- Added scripts for slide management, cleaning, and packing PPTX files, enhancing the overall functionality for users.
- Included a LICENSE file to clarify usage rights and restrictions.
- Created a SKILL.md file to provide an overview and quick reference for PPTX-related tasks.
- Documented various formatting rules, common pitfalls, and design ideas to improve presentation quality.

skills/pptx/scripts/office/schemas/microsoft/wml-2018.xsd

@@ -0,0 +1,14 @@
+ <xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:w12="http://schemas.openxmlformats.org/wordprocessingml/2006/main" elementFormDefault="qualified" attributeFormDefault="qualified" blockDefault="#all" xmlns="http://schemas.microsoft.com/office/word/2018/wordml" targetNamespace="http://schemas.microsoft.com/office/word/2018/wordml">
+   <xsd:import id="w12" namespace="http://schemas.openxmlformats.org/wordprocessingml/2006/main" schemaLocation="../ISO-IEC29500-4_2016/wml.xsd"/>
+   <xsd:complexType name="CT_Extension">
+     <xsd:sequence>
+       <xsd:any processContents="lax"/>
+     </xsd:sequence>
+     <xsd:attribute name="uri" type="xsd:token"/>
+   </xsd:complexType>
+   <xsd:complexType name="CT_ExtensionList">
+     <xsd:sequence>
+       <xsd:element name="ext" type="CT_Extension" minOccurs="0" maxOccurs="unbounded"/>
+     </xsd:sequence>
+   </xsd:complexType>
+ </xsd:schema>