review: make alignments parameter optional

Author: QuietMisdreavus

Sources/SwiftDocC/Model/Rendering/Content/RenderBlockContent.swift

@@ -246,7 +246,7 @@ public enum RenderBlockContent: Equatable {
         public var metadata: RenderContentMetadata?
 
         /// Creates a new table with the given data.
-        public init(header: HeaderType, alignments: [ColumnAlignment]?, rows: [TableRow], extendedData: Set<TableCellExtendedData>, metadata: RenderContentMetadata? = nil) {
+        public init(header: HeaderType, alignments: [ColumnAlignment]? = nil, rows: [TableRow], extendedData: Set<TableCellExtendedData>, metadata: RenderContentMetadata? = nil) {
             self.header = header
             self.rows = rows
             self.extendedData = extendedData

Tests/SwiftDocCTests/Model/RenderContentMetadataTests.swift

@@ -37,7 +37,7 @@ class RenderContentMetadataTests: XCTestCase {
             RenderInlineContent.text("Content"),
         ])
 
-        let table = RenderBlockContent.table(.init(header: .both, alignments: [], rows: [], extendedData: [], metadata: metadata))
+        let table = RenderBlockContent.table(.init(header: .both, rows: [], extendedData: [], metadata: metadata))
         let data = try JSONEncoder().encode(table)
         let roundtrip = try JSONDecoder().decode(RenderBlockContent.self, from: data)