fpdf: add page size a7

fpdf.go

@@ -143,6 +143,7 @@ func fpdfNew(orientationStr, unitStr, sizeStr, fontDirStr string, size SizeType)
 	f.stdPageSizes["a4"] = SizeType{595.28, 841.89}
 	f.stdPageSizes["a5"] = SizeType{420.94, 595.28}
 	f.stdPageSizes["a6"] = SizeType{297.64, 420.94}
+	f.stdPageSizes["a7"] = SizeType{209.76, 297.64}
 	f.stdPageSizes["a2"] = SizeType{1190.55, 1683.78}
 	f.stdPageSizes["a1"] = SizeType{1683.78, 2383.94}
 	f.stdPageSizes["letter"] = SizeType{612, 792}
@@ -239,7 +240,7 @@ func NewCustom(init *InitType) (f *Fpdf) {
 // string will be replaced with "mm".
 //
 // sizeStr specifies the page size. Acceptable values are "A1", "A2", "A3", "A4", "A5",
-// "A6", "Letter", "Legal", or "Tabloid". An empty string will be replaced with "A4".
+// "A6", "A7", "Letter", "Legal", or "Tabloid". An empty string will be replaced with "A4".
 //
 // fontDirStr specifies the file system location in which font resources will
 // be found. An empty string is replaced with ".". This argument only needs to