README.md: Fix MD034 warnings

The following warnings are generated by using markdownlint analysis:
```
MD034/no-bare-urls Bare URL used [Context: "openbmc@lists.ozlabs.org"]
MD034/no-bare-urls Bare URL used [Context: "https://discord.gg/69Km47zH98"]
```
Refer to markdown-lint [1] to fix MD034
[1]: https://github.com/updownpress/markdown-lint/blob/master/rules/034-no-bare-urls.md

Signed-off-by: George Liu <liuxiwei@ieisystem.com>
Change-Id: Id5398d4ddf6e2e157e91e40b69ce1dcaa8aaf7d6
diff --git a/README.md b/README.md
index 96ac0b3..32d3845 100644
--- a/README.md
+++ b/README.md
@@ -6,8 +6,8 @@
 
 ## Contact
 
-- Email: See [OWNERS](OWNERS). Please also Cc openbmc@lists.ozlabs.org
-- Discord: #mctp on https://discord.gg/69Km47zH98
+- Email: See [OWNERS](OWNERS). Please also Cc <openbmc@lists.ozlabs.org>
+- Discord: #mctp on <https://discord.gg/69Km47zH98>
 - IRC: #openbmc on Freenode
 
 ## API/ABI Stability