FEATURE: Ability to build a table in the composer

- Adds a button to the composer tools which triggers a modal window for a table builder
- Table builder contains fields to add table contents, as well as buttons to align contents, and add additional tables/rows

javascripts/discourse/templates/components/body-row.hbs

@@ -0,0 +1,20 @@
+<div class="body-row">
+  <Input
+    @value={{bodyRowValue}}
+    @class="table-builder-input"
+    @placeholderKey={{theme-prefix "discourse_table_builder.modal.body"}}
+    {{on "change" this.addBodyValue}}
+  />
+  <DButton
+    @icon="plus"
+    @title={{theme-prefix "discourse_table_builder.modal.buttons.add_row"}}
+    @action={{action "addRow"}}
+  />
+  <DButton
+    @icon="trash-alt"
+    @class="btn-danger"
+    @title={{theme-prefix "discourse_table_builder.modal.buttons.remove_row"}}
+    @action={{action "removeRow"}}
+    @disabled={{this.disableRemoveRow}}
+  />
+</div>

javascripts/discourse/templates/components/header-column.hbs

@@ -0,0 +1,62 @@
+<div class="header-column">
+  <div class="header-row">
+    <Input
+      @value={{columnHeaderValue}}
+      @class="table-builder-input"
+      @id="header-column-{{@columnId}}"
+      @placeholderKey={{theme-prefix "discourse_table_builder.modal.header"}}
+      {{on "change" this.addColumnHeader}}
+    />
+    <div class="body-inputs">
+      {{#each @column.rows as |item|}}
+        <BodyRow
+          @addRow={{this.addRow}}
+          @columnId={{@columnId}}
+          @allRows={{@column.rows}}
+          @row={{item}}
+          @removeRow={{this.removeRow}}
+          @setRowValue={{this.setRowValue}}
+        />
+      {{/each}}
+    </div>
+
+  </div>
+  <div class="column-action-buttons column-aligned-{{this.alignment}}">
+    <DButton
+      @icon="align-left"
+      @class="btn-align-left"
+      @title={{theme-prefix "discourse_table_builder.modal.buttons.align_left"}}
+      @action={{action "alignColumn" "left"}}
+    />
+    <DButton
+      @icon="align-center"
+      @class="btn-align-center"
+      @title={{theme-prefix
+        "discourse_table_builder.modal.buttons.align_center"
+      }}
+      @action={{action "alignColumn" "center"}}
+    />
+    <DButton
+      @icon="align-right"
+      @class="btn-align-right"
+      @title={{theme-prefix
+        "discourse_table_builder.modal.buttons.align_right"
+      }}
+      @action={{action "alignColumn" "right"}}
+    />
+    <DButton
+      @icon="trash-alt"
+      @class="btn-danger"
+      @action={{action "removeColumn"}}
+      @title={{theme-prefix
+        "discourse_table_builder.modal.buttons.remove_column"
+      }}
+      @disabled={{this.disableRemoveColumn}}
+    />
+    <DButton
+      @icon="plus"
+      @action={{action "addColumn"}}
+      @title={{theme-prefix "discourse_table_builder.modal.buttons.add_column"}}
+    />
+  </div>
+</div>

javascripts/discourse/templates/modal/table-builder-modal.hbs

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+<DModalBody
+  @title={{theme-prefix "discourse_table_builder.modal.title"}}
+  @class="table-builder-modal"
+>
+  <form id="insert-markdown-table-form" {{action "createTable" on="submit"}}>
+    <section class="header-section">
+      <div class="table-header-fields">
+        {{#each this.tableItems as |item|}}
+          <HeaderColumn
+            @column={{item}}
+            @columnId={{item.column}}
+            @tableItems={{this.tableItems}}
+            @addColumn={{this.addColumn}}
+            @removeColumn={{this.removeColumn}}
+            @setColumnHeader={{this.setColumnHeader}}
+            @addRow={{this.addRow}}
+            @removeRow={{this.removeRow}}
+            @setRowValue={{this.setRowValue}}
+            @alignColumn={{this.alignColumn}}
+          />
+        {{/each}}
+      </div>
+    </section>
+  </form>
+</DModalBody>
+
+<div class="modal-footer">
+  <DButton
+    @class="btn-primary"
+    @label={{theme-prefix "discourse_table_builder.modal.create"}}
+    @icon="plus"
+    @action={{action "createTable"}}
+  />
+
+  <DButton
+    @class="btn-flat"
+    @label={{theme-prefix "discourse_table_builder.modal.cancel"}}
+    @action={{action "cancelTableCreation"}}
+  />
+</div>