cmake: Add DESCRIPTION and HOMEPAGE_URL options to project command

`DESCRIPTION` is available in CMake 3.9+.
`HOMEPAGE_URL` is available in CMake 3.12+.

CMakeLists.txt

@@ -7,10 +7,15 @@ if(CMAKE_VERSION VERSION_GREATER 3.14)
   cmake_policy(SET CMP0092 NEW)
 endif()
 
-# The package (a.k.a. release) version is based on semantic versioning 2.0.0 of
-# the API. All changes in experimental modules are treated as
-# backwards-compatible and therefore at most increase the minor version.
-project(libsecp256k1 VERSION 0.3.2 LANGUAGES C)
+project(libsecp256k1
+  # The package (a.k.a. release) version is based on semantic versioning 2.0.0 of
+  # the API. All changes in experimental modules are treated as
+  # backwards-compatible and therefore at most increase the minor version.
+  VERSION 0.3.2
+  DESCRIPTION "Optimized C library for ECDSA signatures and secret/public key operations on curve secp256k1."
+  HOMEPAGE_URL "https://github.com/bitcoin-core/secp256k1"
+  LANGUAGES C
+)
 
 # The library version is based on libtool versioning of the ABI. The set of
 # rules for updating the version can be found here: