feat(): Support easy serialization of custom properties

[asturur]

Description

There is a lot of feedback about easyness serialization of custom properties.
This PR adds a static property to fabricObject where you can store the name of the custom ( or non custom but not exported ) properties you would like to be exported regadless.

In Action

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[github-actions]

Build Stats

file / KB (diff)	bundled	minified
fabric	920.728 (+0.161)	306.754 (-0.156)

[github-actions]

Coverage after merging support-custom-prop-serialization into master will be

85.19%

Coverage Report

File	Stmts	Branches	Funcs	Lines	Uncovered Lines
index.node.ts	14.29%	100%	0%	25%	23, 26, 29, 41, 44, 47
extensions/aligning_guidelines/util
basic.ts	100%	100%	100%	100%
src
ClassRegistry.ts	91.18%	64.29%	100%	97.92%	35, 56
Collection.ts	78.71%	44.62%	87.10%	86.21%	130, 153, 155–157, 159, 169–170, 181, 197, 217, 228, 241, 243, 252, 254, 265, 270, 279, 281, 286–287, 302, 304, 309–310, 329, 333–334, 338–344, 346–348, 350
CommonMethods.ts	91.43%	71.43%	100%	96%	50, 52
Intersection.ts	85.25%	48.91%	100%	97.30%	184–188, 190, 228, 237, 239, 289, 297, 297
Observable.ts	80.63%	53.49%	93.75%	87.88%	144, 153, 156, 168, 170, 175, 68–70, 72, 76, 80, 84–85, 87–91
Point.ts	90.53%	62%	100%	93.90%	104, 117, 148, 157, 179, 197, 206, 216, 225, 236–239, 259, 285, 297, 328, 341, 349, 359, 95
Shadow.ts	89.21%	78.26%	100%	90%	140, 143, 145–150, 159, 196, 199, 206, 223–230, 234–235
cache.ts	84.88%	45.45%	100%	90.14%	57, 59, 71–72, 74–77
config.ts	87.73%	55%	66.67%	94.03%	132, 134–137, 139, 142–143, 147, 152
constants.ts	100%	100%	100%	100%
src/LayoutManager
ActiveSelectionLayoutManager.ts	93.33%	76.92%	85.71%	100%
LayoutManager.ts	90.75%	65.48%	76.92%	99.31%	279, 344, 355
constants.ts	100%	100%	100%	100%
index.ts	48.57%	37.50%	80%	66.67%	1, 1, 1–2, 2, 2–3, 3, 3–4, 4, 4–5, 5, 5, 5–6
types.ts	100%	100%	100%	100%
src/LayoutManager/LayoutStrategies
ClipPathLayout.ts	75%	56.25%	100%	78.95%	39, 41–44, 46–48, 66–69
FitContentLayout.ts	100%	100%	100%	100%
FixedLayout.ts	85.71%	20%	100%	100%	23, 23
LayoutStrategy.ts	87.60%	57.14%	100%	96.51%	46, 54, 73, 73, 75
utils.ts	72.58%	50%	100%	78.72%	29–32, 34–35, 40–44
src/Pattern
Pattern.ts	67.50%	88.57%	80%	63.08%	105–107, 114, 118–119, 119–122, 130–138, 140–141, 143, 153–164, 174, 176–181, 183–188, 190–199, 203–206, 209–210, 212–214, 216–218, 218–221, 33, 37
src/brushes
BaseBrush.ts	89.33%	91.67%	100%	88.55%	110, 115, 124–125, 130, 135, 143, 146, 155–160, 99
CircleBrush.ts	52.10%	12.50%	12.50%	58.25%	100–108, 108–118, 122, 130–139, 55, 67, 69, 76, 76, 78–79, 79, 83, 85–86, 92–98
PatternBrush.ts	97.06%	87.50%	100%	100%	21
PencilBrush.ts	91.06%	82.35%	100%	93.81%	122–123, 152, 152–154, 176, 176, 276, 280, 285–286, 68–69, 84–85
SprayBrush.ts	0%	0%	0%	0%	107, 107, 107, 107, 107–108, 110–111, 118–119, 121, 123–127, 136, 140–141, 141, 148, 148, 148–151, 153–156, 160–161, 163, 165–168, 17, 171, 178–179, 18, 181, 183–184, 186, 193–194, 196–197, 20, 200, 200, 207, 207, 21, 211, 22, 22, 22–24, 28, 32, 39, 46, 53, 60, 67, 84–86, 94–96, 98–99
src/canvas
Canvas.ts	75.43%	39.53%	92.86%	84.95%	1000, 1005, 1009, 1013–1014, 1019, 1064–1069, 1106, 1127, 1129, 1131, 1138, 1141, 1204–1208, 1287–1291, 1318, 1335, 1381–1398, 1404–1409, 1412–1413, 1415, 1419, 1421–1422, 1424–1426, 1430, 1432, 1434–1436, 1439–1444, 1447–1449, 1452, 1454, 1468, 1475, 1477–1488, 1490–1493, 1493–1494, 1496–1497, 1501–1502, 1505–1506, 1509–1511, 1514, 329, 354, 370, 389, 444, 560–564, 567–568, 570, 580, 583–584, 586, 589–591, 603, 610–614, 616–621, 623–627, 660, 662, 669–673, 675–680, 682, 684–685, 687–690, 692–693, 748, 784–787, 790, 792, 795, 797, 799, 825, 887–888, 933–934, 936–937, 939, 948–954, 957, 965–971, 973, 975, 996–997
CanvasOptions.ts	100%	100%	100%	100%
SelectableCanvas.ts	85.45%	54.22%	100%	94.39%	1006, 1008–1009, 1026, 1035, 1103–1107, 1153–1154, 1156–1157, 1159, 1186, 1188–1189, 1189, 1191, 1233, 1235, 1237, 1253, 1255, 1283, 1286, 1329–1336, 1339, 1342, 1351–1352, 1356–1365, 1369, 1371–1372, 1378–1383, 1387, 340–342, 346, 376, 398, 476, 527, 529, 605, 610, 687, 715
StaticCanvas.ts	75.74%	69.11%	98.91%	75.38%	1000, 1006, 1009, 1011, 1013, 1021, 1023–1029, 1039, 1042, 1045–1051, 1053–1054, 1056–1077, 1084–1086, 1088, 1096, 1102, 1104, 1104–1105, 1105–1106, 1108, 1108–1113, 1126, 1131–1133, 1137, 1141, 1143, 1145, 1150–1154, 1156, 1158–1161, 1164, 1166, 1175, 1177–1178, 1185–1188, 1190, 1196–1199, 1203–1204, 1214, 1220–1222, 1224–1229, 1229, 1229–1233, 1233, 1233–1238, 1240–1247, 1276–1277, 1279–1284, 1286–1292, 1296, 1298–1311, 1319–1320, 1330, 1341, 1382–1386, 1388, 1390, 1392–1396, 1415, 1431, 1448, 1468, 1501, 1505, 1516–1518, 425, 436,