See whether relative links work for the documentation.

When BoringSSL is imported elsewhere, it would be nice for the links to
be relative, but I'm not sure if that'll work on Gerrit. This change
will try it and can be reverted if
https://boringssl.googlesource.com/boringssl breaks.

Change-Id: I17e056331677923b76fb8852ce8c00e2a4674af4
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/55685
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: Adam Langley <agl@google.com>

README.md

@@ -30,13 +30,13 @@ Project links:
 
 There are other files in this directory which might be helpful:
 
-  * [PORTING.md](/PORTING.md): how to port OpenSSL-using code to BoringSSL.
-  * [BUILDING.md](/BUILDING.md): how to build BoringSSL
-  * [INCORPORATING.md](/INCORPORATING.md): how to incorporate BoringSSL into a project.
-  * [API-CONVENTIONS.md](/API-CONVENTIONS.md): general API conventions for BoringSSL consumers and developers.
-  * [STYLE.md](/STYLE.md): rules and guidelines for coding style.
+  * [PORTING.md](./PORTING.md): how to port OpenSSL-using code to BoringSSL.
+  * [BUILDING.md](./BUILDING.md): how to build BoringSSL
+  * [INCORPORATING.md](./INCORPORATING.md): how to incorporate BoringSSL into a project.
+  * [API-CONVENTIONS.md](./API-CONVENTIONS.md): general API conventions for BoringSSL consumers and developers.
+  * [STYLE.md](./STYLE.md): rules and guidelines for coding style.
   * include/openssl: public headers with API documentation in comments. Also [available online](https://commondatastorage.googleapis.com/chromium-boringssl-docs/headers.html).
-  * [FUZZING.md](/FUZZING.md): information about fuzzing BoringSSL.
-  * [CONTRIBUTING.md](/CONTRIBUTING.md): how to contribute to BoringSSL.
-  * [BREAKING-CHANGES.md](/BREAKING-CHANGES.md): notes on potentially-breaking changes.
-  * [SANDBOXING.md](/SANDBOXING.md): notes on using BoringSSL in a sandboxed environment.
+  * [FUZZING.md](./FUZZING.md): information about fuzzing BoringSSL.
+  * [CONTRIBUTING.md](./CONTRIBUTING.md): how to contribute to BoringSSL.
+  * [BREAKING-CHANGES.md](./BREAKING-CHANGES.md): notes on potentially-breaking changes.
+  * [SANDBOXING.md](./SANDBOXING.md): notes on using BoringSSL in a sandboxed environment.