Let client call hover request

Part of #1186

Author: Philippe Gil

source/gpr/lsp-gpr_handlers.adb

@@ -489,10 +489,15 @@ package body LSP.GPR_Handlers is
       Value : LSP.Structures.InitializeParams)
    is
       Response : LSP.Structures.InitializeResult;
+      Capabilities : LSP.Structures.ServerCapabilities;
 
    begin
       Self.File_Reader := LSP.GPR_File_Readers.Create (Self'Unchecked_Access);
 
+      Capabilities.hoverProvider := LSP.Constants.True;
+
+      Response.capabilities := Capabilities;
+
       Response.capabilities.textDocumentSync :=
         (Is_Set => True,
          Value  => (Is_TextDocumentSyncOptions => True,