Add Odd-Even Merge operation mode (#1445)

* Add ODD_EVEN_MERGE sort type

* Add process method to merge odd and even PDF pages

* Add test cases for Odd-Even merge method

* Add Odd-Even Merge mode in PDF Organizer webpage

This also add a new translatable text message variable pdfOrganiser.mode.10 with translation for english and german

* Add ODD_EVEN_MERGE documentation to RearrangePagesRequest

* Add english translation for pdfOrganiser.mode.10

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Co-authored-by: Anthony Stirling <77850077+Frooodle@users.noreply.github.com>

src/main/java/stirling/software/SPDF/model/SortTypes.java

@@ -6,6 +6,7 @@ public enum SortTypes {
     BOOKLET_SORT,
     SIDE_STITCH_BOOKLET_SORT,
     ODD_EVEN_SPLIT,
+    ODD_EVEN_MERGE,
     REMOVE_FIRST,
     REMOVE_LAST,
     REMOVE_FIRST_AND_LAST,

src/main/java/stirling/software/SPDF/model/api/general/RearrangePagesRequest.java

@@ -19,6 +19,7 @@ public class RearrangePagesRequest extends PDFWithPageNums {
                             + "DUPLEX_SORT: Sorts pages as if all fronts were scanned then all backs in reverse (1, n, 2, n-1, ...). "
                             + "BOOKLET_SORT: Arranges pages for booklet printing (last, first, second, second last, ...).\n"
                             + "ODD_EVEN_SPLIT: Splits and arranges pages into odd and even numbered pages.\n"
+                            + "ODD_EVEN_MERGE: Merges pages and organises them alternately into odd and even pages.\n"
                             + "REMOVE_FIRST: Removes the first page.\n"
                             + "REMOVE_LAST: Removes the last page.\n"
                             + "REMOVE_FIRST_AND_LAST: Removes both the first and the last pages.\n")