[M108 Migration][API] Add PWA APIs as public API

[M108 Migration][API] Add PWA APIs as public API

This patch adds below PWA APIs as public API.

- Ewk_View_Request_Manifest_Callback
- ewk_view_request_manifest
- Ewk_View_Request_Manifest
- Ewk_View_Orientation_Type
- Ewk_View_Web_Display_Mode
- ewk_manifest_short_name_get
- ewk_manifest_name_get
- ewk_manifest_start_url_get
- ewk_manifest_orientation_type_get
- ewk_manifest_web_display_mode_get
- ewk_manifest_theme_color_get
- ewk_manifest_background_color_get
- ewk_manifest_icons_count_get
- ewk_manifest_icons_src_get
- ewk_manifest_icons_type_get
- ewk_manifest_icons_sizes_count_get
- ewk_manifest_icons_width_get
- ewk_manifest_icons_height_get

References: https://review.tizen.org/gerrit/272868/

Change-Id: Ie4fc7a2e90ca0a5d21b16863e7469e90f4b5d2e7
Signed-off-by: Ayush Kumar <ayush.k123@samsung.com>