Using GGG: link to 'cover-letter' anchor in MyFirstContribution

We refer readers to the MyFirstContribution tutorial when mentioning the
cover letter. Let's do even better and link directly to the section of
the tutorial that explains the purpose and content of the cover letter.

Author: phil-blain

index.html

@@ -102,7 +102,7 @@ <h2>How can you use GitGitGadget?</h2>
 				Good, now is the time to direct your web browser to <a href="https://github.com/gitgitgadget/git">https://github.com/gitgitgadget/git</a> (or to <a href="https://github.com/git/git">https://github.com/git/git</a> ) and to open a Pull Request.
 				A few things to note about a GitGitGadget Pull Request:
 				<ul>
-					<li>Please make sure to use a descriptive title and description; GitGitGadget will use these as the subject and body of the cover letter (check out the <a href="https://git-scm.com/docs/MyFirstContribution">MyFirstContribution</a> tutorial if you are not familiar with this terminology).</li>
+					<li>Please make sure to use a descriptive title and description; GitGitGadget will use these as the subject and body of the cover letter (check out the <a href="https://git-scm.com/docs/MyFirstContribution#cover-letter">MyFirstContribution</a> tutorial if you are not familiar with this terminology).</li>
 					<li>You can CC potential reviewers by adding a footer to the PR description with the following syntax:</br>
 					<code>CC: Revi Ewer &lt;revi.ewer@some.domain&gt;, Ill Takalook &lt;ill.takalook@other.domain&gt;</code>
 					</li>