Correct some markup issues (#673)

Author: johnzhou721

content/contributing/first-time/github-notifications-101/contents.lr

@@ -26,7 +26,7 @@ handle things.
 
 Each repo has a number of notification settings:
 
-- Watching - you get notifications for \_\_everything\_\_. Any issue,
+- Watching - you get notifications for __everything__. Any issue,
   any Pull Request, any comment. This is helpful if you really really
   super duper care about a repo
 - Not Watching - you will only get notifications if you're mentioned, or
@@ -41,7 +41,7 @@ You can check what repos you're watching across all of GitHub from the
 GitHub emails are rich in information that can help you filter out what
 you care about and what you don't.
 
-Emails will have the subject line of repo in question
+An email's subject line includes the name of the repo in question.
 
 - For example, `[beeware/batavia] Add a new function` would be a
   notification from the repo Batavia
@@ -61,7 +61,7 @@ If you're only subscribed to a repo:
 If you want to mute a specific thread, you can click the 'Unsubscribe'
 button on any issue or pull request.
 
-If you get email, you can click on the 'Mute this thread'.
+If you get email, you can click on 'Mute this thread'.
 
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 gutter: