Make PyInstaller bundle all necessary binaries for the mip library.

Note that the release command has an additional parameter, as
detailed in the README.

Addresses coin-or/python-mip#76, and will
become obsolete when
pyinstaller/pyinstaller#4762 makes it into
the pyinstaller release.

README.md

@@ -44,7 +44,7 @@ To make a single file executable, we use [PyInstaller](https://pyinstaller.readt
 The command is:
 
 ```
-python -m eel script.py web --onefile --noconsole
+python -m eel script.py web --additional-hooks-dir=. --onefile --noconsole
 ```
 
 **Platform** means Windows, Mac OS X or Linux.  So if you run the above command on Linux, you can give the file to someone else running Linux.  So if the person who wants the app is running Windows, you need to run the above command on Windows.

hook-mip.py

@@ -0,0 +1,15 @@
+# Ensures that PyInstaller copies the CBC binaries for the mip library.
+# See https://github.com/coin-or/python-mip/issues/76.
+# Should become obsolete once https://github.com/pyinstaller/pyinstaller/pull/4762
+# gets merged and makes it into the pyinstaller release.
+
+import os
+from PyInstaller.utils.hooks import get_package_paths
+
+datas = []
+_, mip_path = get_package_paths("mip")
+lib_path = os.path.join(mip_path, "libraries")
+
+for f in os.listdir(lib_path):
+    if f.endswith(".so") or f.endswith(".dll") or f.endswith(".dylib"):
+        datas.append((os.path.join(lib_path, f), "mip/libraries"))