feat: Working on node builder

Sources/CliDoc/Nodes/ShellCommand.swift

@@ -0,0 +1,41 @@
+public struct ShellCommand: NodeRepresentable {
+
+  @usableFromInline
+  let symbol: any NodeRepresentable
+
+  @usableFromInline
+  let command: any NodeRepresentable
+
+  @inlinable
+  public init(
+    @NodeBuilder symbol: () -> any NodeRepresentable,
+    @NodeBuilder command: () -> any NodeRepresentable
+  ) {
+    self.symbol = symbol()
+    self.command = command()
+  }
+
+  @inlinable
+  public init(
+    symbol: String = "  $",
+    @NodeBuilder command: () -> any NodeRepresentable
+  ) {
+    self.init { symbol } command: { command() }
+  }
+
+  @inlinable
+  public init(
+    symbol: String = "  $",
+    command: String
+  ) {
+    self.init { symbol } command: { command }
+  }
+
+  @inlinable
+  public func render() -> String {
+    Group(separator: " ") {
+      symbol
+      command
+    }.render()
+  }
+}