test_debug_server.trace_websocket_sends_trace_data is failing
occasionally with the following message:

    [ RUN      ] test_debug_server.trace_websocket_sends_trace_data
    .../test/test-debug-server.cpp:464: Failure
    Actual function call count doesn't match EXPECT_CALL(v, visit_init_event(::testing::Field( &trace_stream_event_visitor::init_event::version, ::testing::StrEq("2.10.0"))))...
             Expected: to be called once
               Actual: never called - unsatisfied and active
    .../test/test-debug-server.cpp:461: Failure
    Actual function call count doesn't match EXPECT_CALL(v, visit_packet_header(::testing::_))...
             Expected: to be called once
               Actual: never called - unsatisfied and active
    .../test/test-debug-server.cpp:464: Failure
    Actual function call count doesn't match EXPECT_CALL(v, visit_init_event(::testing::Field( &trace_stream_event_visitor::init_event::version, ::testing::StrEq("2.10.0"))))...
             Expected: to be called once
               Actual: never called - unsatisfied and active
    .../test/test-debug-server.cpp:461: Failure
    Actual function call count doesn't match EXPECT_CALL(v, visit_packet_header(::testing::_))...
             Expected: to be called once
               Actual: never called - unsatisfied and active
    .../test/test-debug-server.cpp:464: Failure
    Actual function call count doesn't match EXPECT_CALL(v, visit_init_event(::testing::Field( &trace_stream_event_visitor::init_event::version, ::testing::StrEq("2.10.0"))))...
             Expected: to be called once
               Actual: never called - unsatisfied and active
    .../test/test-debug-server.cpp:461: Failure
    Actual function call count doesn't match EXPECT_CALL(v, visit_packet_header(::testing::_))...
             Expected: to be called once
               Actual: never called - unsatisfied and active
    .../test/test-debug-server.cpp:482: Failure
    Value of: delegate.received_thread_indexes
    Expected: has 3 elements and there exists some permutation of elements such that:
     - element #0 is equal to 1, and
     - element #1 is equal to 2, and
     - element #2 is equal to 3
      Actual: { 3, 1, 2, 3, 1, 2 }, which has 6 elements
    expected three streams: main thread, other thread, debug server thread
    [  FAILED  ] test_debug_server.trace_websocket_sends_trace_data (1 ms)

These failures are caused by the test not handling empty messages
properly. Hackily fix the flaky failure by ignoring empty messages in
the test.

> Rule #2: use bold and italic as little as possible.
> https://practicaltypography.com/bold-or-italic.html

The releases page has invalid HTML:

    <a href="#2.15.0">2.15.0 (2023-07-18)<a>

Fix the closing 'a' by telling the Markdown tool that it's a closing
tag:

    <a href="#2.15.0">2.15.0 (2023-07-18)</a>