DOC: use unicode emoji's in the shared library support table

Author: rgommers

docs/how-to-guides/shared-libraries.rst

@@ -24,15 +24,18 @@ this ``libdir`` in this guide) or to a location in ``site-packages`` within the
 Python package install tree. All these scenarios are (or will be) supported,
 with some caveats:
 
-+-----------------------+------------------+---------+-------+-------+
-| shared library source | install location | Windows | macOS | Linux |
-+=======================+==================+=========+=======+=======+
-| internal              | libdir           | no (1)  | ✓     | ✓     |
-+-----------------------+------------------+---------+-------+-------+
-| internal              | site-packages    | ✓       | ✓     | ✓     |
-+-----------------------+------------------+---------+-------+-------+
-| external              | n/a              | ✓ (2)   | ✓     | ✓     |
-+-----------------------+------------------+---------+-------+-------+
++-----------------------+------------------+-------------+-------------+---------+
+| shared library source | install location | Windows     | macOS       | Linux   |
++=======================+==================+=============+=============+=========+
+| internal              | libdir           |  |wip| (1)  |   |check|   | |check| |
++-----------------------+------------------+-------------+-------------+---------+
+| internal              | site-packages    |  |check|    |   |check|   | |check| |
++-----------------------+------------------+-------------+-------------+---------+
+| external              | n/a              | |check| (2) |   |check|   | |check| |
++-----------------------+------------------+-------------+-------------+---------+
+
+.. |check| unicode:: x1F5F9
+.. |wip| unicode:: x1F6A7
 
 .. TODO: add subproject as a source