Merge branch 'feature/multiple-sections' of https://github.com/h4buli/docx into feat/multiple-headers

# Conflicts:
#	src/export/packer/compiler.ts
#	src/file/content-types/content-types.ts
#	src/file/document/body/section-properties/header-reference/header-reference.ts
#	src/file/document/body/section-properties/section-properties.ts
#	src/file/file.ts
#	src/file/media/media.ts

src/file/header-wrapper.ts

@@ -9,8 +9,8 @@ export class FirstPageHeaderWrapper {
     private readonly header: Header;
     private readonly relationships: Relationships;
 
-    constructor(private readonly media: Media) {
-        this.header = new Header();
+    constructor(private readonly media: Media, referenceId: number) {
+        this.header = new Header(referenceId);
         this.relationships = new Relationships();
     }
 
@@ -59,8 +59,8 @@ export class HeaderWrapper {
     private readonly header: Header;
     private readonly relationships: Relationships;
 
-    constructor(private readonly media: Media) {
-        this.header = new Header();
+    constructor(private readonly media: Media, referenceId: number) {
+        this.header = new Header(referenceId);
         this.relationships = new Relationships();
     }