feat: tablerowloop object

See: https://www.rubydoc.info/gems/liquid/Liquid/TablerowloopDrop

src/drop/tablerowloop-drop.ts

@@ -0,0 +1,25 @@
+import { ForloopDrop } from './forloop-drop'
+
+export class TablerowloopDrop extends ForloopDrop {
+  private cols: number
+  constructor (length: number, cols: number) {
+    super(length)
+    this.length = length
+    this.cols = cols
+  }
+  row () {
+    return Math.floor(this.i / this.cols) + 1
+  }
+  col0 () {
+    return (this.i % this.cols)
+  }
+  col () {
+    return this.col0() + 1
+  }
+  col_first () {  // eslint-disable-line
+    return this.col0() === 0
+  }
+  col_last () { // eslint-disable-line
+    return this.col() === this.cols
+  }
+}