RoosterJs 8.50.0 and RoosterJs Content Model 0.9.0

Bug fix

• Fix table inserter for merged vertical cells (#1869)
• Dismiss TableEditors when mouse is moved out of the editor 9#1863)
• Fix Table Inserter Color in Dark Mode (#1877)
• Add back onExternalContentTransform (#1874)
• Improve dark color transform behavior (#1878)
• Handle dark colors for table background color (#1881)

Content Model

• Content Model Copy/Paste improvement (#1856, #1862, #1867, #1875, #1866, #1882)
• Improve performance of Delete/Backspace handling (#1870, #1873)
• Fix focus issue (#1872)
• Ignore empty paragraph when turn on list (#1868)
• Fix header level issue (#1876)
• Fix page scroll issue when change color multiple times (#1879)
• Content fidelity improvement (#1885, #1886, #1889, #1891, #1892)

Engineering improvement

• use importHelpers to reduce pack size (#1865)
• Enable strict mode for all dev code (#1883)
• Split demo site into two parts (#1880)

Interface changes

• New parameter of VTable.writeBack()
  • darkColorHandler: An object to handle dark background colors, if not passed the cell background color will not be set