#14 make buffer mappings configurable

[hoschi]

This makes buffer mappings configurable. Set own mappings by:

"------------------------------
"yode-nvim
"------------------------------
lua << EOF
require('yode-nvim').setup({
    handlers = {
        onSeditorBufCal = function()
            vim.cmd([[
                imap <buffer> <leader>bly <esc>:YodeGoToAlternateBuffer t<cr>
            ]])
        end,
    },
})
EOF

Disable the mappings by:

"------------------------------
"yode-nvim
"------------------------------
lua << EOF
require('yode-nvim').setup({
    handlers = {
        onSeditorBufCal = function()
        end,
    },
})
EOF