Doxygen: rename all .dox files to end with .md

Using a standard ending here will let other tools that expect
markdown understand our output here.

This commit was automatically generated with:

   for fn in $(find src -name '*.dox'); do \
      git mv "$fn" "${fn%.dox}.md"; \
   done

1 files changed, 11 insertions, 0 deletions

diff --git a/src/lib/tls/lib_tls.md b/src/lib/tls/lib_tls.md
new file mode 100644
index 0000000000..26fea723f9
--- /dev/null
+++ b/src/lib/tls/lib_tls.md
@@ -0,0 +1,11 @@
+@dir /lib/tls
+@brief lib/tls: TLS library wrappers
+
+This module has compatibility wrappers around the library (NSS or OpenSSL,
+depending on configuration) that Tor uses to implement the TLS link security
+protocol.
+
+It also implements the logic for some legacy TLS protocol usage we used to
+support in old versions of Tor, involving conditional delivery of certificate
+chains (v1 link protocol) and conditional renegotiation (v2 link protocol).
+