Add language fences around markdown code blocks #1049

Job	Run time
static analysis (Elixir 1.15.x \| Erlang/OTP 25.x)	23s
mix test windows (Elixir 1.13.x \| Erlang/OTP 22.x)	9m 11s
mix test (Elixir 1.13.x \| Erlang/OTP 22.x)	5m 20s
mix test windows (Elixir 1.13.x \| Erlang/OTP 23.x)	8m 32s
mix test (Elixir 1.13.x \| Erlang/OTP 23.x)	6m 2s
mix test windows (Elixir 1.13.x \| Erlang/OTP 24.x)	6m 26s
mix test (Elixir 1.13.x \| Erlang/OTP 24.x)	4m 23s
mix test windows (Elixir 1.13.x \| Erlang/OTP 25.x)	5m 41s
mix test (Elixir 1.13.x \| Erlang/OTP 25.x)	3m 55s
mix test windows (Elixir 1.14.x \| Erlang/OTP 23.x)	8m 41s
mix test (Elixir 1.14.x \| Erlang/OTP 23.x)	7m 16s
mix test windows (Elixir 1.14.x \| Erlang/OTP 24.x)	8m 9s
mix test (Elixir 1.14.x \| Erlang/OTP 24.x)	4m 32s
mix test windows (Elixir 1.14.x \| Erlang/OTP 25.x)	5m 45s
mix test (Elixir 1.14.x \| Erlang/OTP 25.x)	4m 9s
mix test windows (Elixir 1.15.x \| Erlang/OTP 24.x)	6m 40s
mix test (Elixir 1.15.x \| Erlang/OTP 24.x)	5m 52s
mix test windows (Elixir 1.15.x \| Erlang/OTP 25.x)	6m 48s
mix test (Elixir 1.15.x \| Erlang/OTP 25.x)	4m 43s
	1h 52m 28s

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