docs: use footnotes

docs/failures.md

@@ -61,7 +61,13 @@ int main(int argc, char* argv[]) {
 ```
 
 By default, glog tries to dump the stacktrace and calls `#!cpp std::abort`. The
-stacktrace is generated only when running the application on a system supported
-by glog. Currently, glog supports x86, x86_64, PowerPC architectures,
-`libunwind`, and the Debug Help Library (`dbghelp`) on Windows for extracting
-the stack trace.
+stacktrace is generated only when running the application on a system
+supported[^1] by glog.
+
+[^1]: To extract the stack trace, glog currently supports the following targets:
+
+    * x86, x86_64,
+    * PowerPC architectures,
+    * `libunwind`,
+    * and the Debug Help Library (`dbghelp`) on Windows.
+

docs/windows.md

@@ -34,11 +34,11 @@ google::FlushLogFiles(google::GLOG_ERROR);
 ```
 
 If you don't need `ERROR` defined by `windows.h`, there are a couple of more
-workarounds which sometimes don't work:
+workarounds which sometimes don't work[^1]:
 
 -  `#!cpp #define WIN32_LEAN_AND_MEAN` or `NOGDI` **before**
    `#!cpp #include <windows.h>`.
 -  `#!cpp #undef ERROR` **after** `#!cpp #include <windows.h>`.
 
-See [this issue](http://code.google.com/p/google-glog/issues/detail?id=33) for
-more detail.
+[^1]: For more information refer to [this
+      issue](http://code.google.com/p/google-glog/issues/detail?id=33).

mkdocs.yml

@@ -9,6 +9,7 @@ markdown_extensions:
   - admonition
   - attr_list
   - def_list
+  - footnotes
   - md_in_html
   - pymdownx.details
   - pymdownx.highlight: