fix(migration): updated Trello color map to import all labels (#2178)

Trello has [added 20 color variants](https://www.atlassian.com/blog/trello/20-new-trello-label-colors) that were not imported, added them. Also added a fallback to save labels even if the color is not mapped yet.

Resolves https://community.vikunja.io/t/get-info-about-importation-trello/1968/16
Reviewed-on: https://kolaente.dev/vikunja/vikunja/pulls/2178
Reviewed-by: konrad <k@knt.li>
Co-authored-by: Hangya <ronkayj@gmail.com>
Co-committed-by: Hangya <ronkayj@gmail.com>

pkg/modules/migration/trello/trello_test.go

@@ -137,6 +137,16 @@ func TestConvertTrelloToVikunja(t *testing.T) {
 									Name:  "Label 3",
 									Color: "blue",
 								},
+								{
+									ID:    "ide4",
+									Name:  "Label 4",
+									Color: "green_dark",
+								},
+								{
+									ID:    "ide5",
+									Name:  "Label 5",
+									Color: "doesnotexist",
+								},
 							},
 						},
 						{
@@ -294,6 +304,14 @@ func TestConvertTrelloToVikunja(t *testing.T) {
 								Title:    "Label 3",
 								HexColor: trelloColorMap["blue"],
 							},
+							{
+								Title:    "Label 4",
+								HexColor: trelloColorMap["green_dark"],
+							},
+							{
+								Title:    "Label 5",
+								HexColor: trelloColorMap["transparent"],
+							},
 						},
 					},
 				},