added dropdowns documentation

docs/en/UI/AspNetCore/Tag-Helpers/Dropdowns.md

@@ -0,0 +1,97 @@
+# Dropdowns
+
+## Introduction
+
+`abp-dropdown` is the main container for dropdown content. 
+
+Basic usage:
+
+````xml
+<abp-dropdown>
+    <abp-dropdown-button text="Dropdown button" />
+    <abp-dropdown-menu>
+        <abp-dropdown-item href="#">Action</abp-dropdown-item>
+        <abp-dropdown-item href="#">Another action</abp-dropdown-item>
+        <abp-dropdown-item href="#">Something else here</abp-dropdown-item>
+    </abp-dropdown-menu>
+</abp-dropdown>
+````
+
+
+
+## Demo
+
+See the [dropdown demo page](https://bootstrap-taghelpers.abp.io/Components/Dropdowns) to see it in action.
+
+## Attributes
+
+### direction
+
+A value indicates which direction the dropdown buttons will be displayed to. Should be one of the following values:
+
+* `Down` (default value)
+* `Up`
+* `Right`
+* `Left`
+
+### dropdown-style
+
+A value indicates if an `abp-dropdown-button` will have split icon for dropdown. Should be one of the following values:
+
+* `Single` (default value)
+* `Split`
+
+
+
+## Menu items
+
+`abp-dropdown-menu` is the main container for dropdown menu items. 
+
+Basic usage:
+
+````xml
+<abp-dropdown>
+    <abp-dropdown-button button-type="Secondary" text="Dropdown"/>
+    <abp-dropdown-menu>
+        <abp-dropdown-header>Dropdown Header</abp-dropdown-header>
+        <abp-dropdown-item href="#">Action</abp-dropdown-item>
+        <abp-dropdown-item active="true" href="#">Active action</abp-dropdown-item>
+        <abp-dropdown-item disabled="true" href="#">Disabled action</abp-dropdown-item>
+        <abp-dropdown-divider/>
+        <abp-dropdown-item-text>Dropdown Item Text</abp-dropdown-item-text>
+        <abp-dropdown-item href="#">Something else here</abp-dropdown-item>
+    </abp-dropdown-menu>
+</abp-dropdown>
+````
+
+## Attributes
+
+### align
+
+A value indicates which direction `abp-dropdown-menu` items will be aligned to. Should be one of the following values:
+
+* `Left` (default value)
+* `Right`
+
+### Additional content
+
+`abp-dropdown-menu` can also contain additional HTML elements like headings, paragraphs, dividers or form element.
+
+Example:
+
+````xml
+<abp-dropdown >
+    <abp-dropdown-button button-type="Secondary" text="Dropdown With Form"/>
+    <abp-dropdown-menu>
+        <form class="px-4 py-3">
+            <abp-input asp-for="EmailAddress"></abp-input>
+            <abp-input asp-for="Password"></abp-input>
+            <abp-input asp-for="RememberMe"></abp-input>
+            <abp-button button-type="Primary" text="Sign In" type="submit" />
+        </form>
+        <abp-dropdown-divider></abp-dropdown-divider>
+        <abp-dropdown-item href="#">New around here? Sign up</abp-dropdown-item>
+        <abp-dropdown-item href="#">Forgot password?</abp-dropdown-item>
+    </abp-dropdown-menu>
+</abp-dropdown>
+````