splited VHDL memo

docs/memo/adder.md

docs/memo/assert.md

docs/memo/async-reset.md

docs/memo/counter.md

docs/memo/fsm.md

docs/memo/instance.md

docs/memo/multiplexer.md

docs/memo/multiplier.md

docs/memo/non-synthesizable-vhdl.md

docs/memo/numeric-std.md

docs/memo/operators.md

docs/memo/ram.md

docs/memo/register.md

docs/memo/synthesizable-vhdl.md

docs/memo/testbench.md

docs/memo/text-file.md

docs/memo/types.md

docs/vhdl/loto.md

docs/vhdl/sit212.md

mkdocs.yml