Add man page for llvm-readobj

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179244 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/CommandGuide/index.rst b/docs/CommandGuide/index.rst
index ac8a944..b3b4bc3 100644
--- a/docs/CommandGuide/index.rst
+++ b/docs/CommandGuide/index.rst
@@ -50,3 +50,4 @@
    tblgen
    lit
    llvm-build
+   llvm-readobj