feat: add fennel-ls support

[gh-liu]

Untested on windows.

[glepnir]

does this server not support windows?

[gh-liu]

does this server not support windows?

does this server not support windows?

I guess it's possible, but I haven't tried it yet.

[glepnir]

so we can simply add the server cmd in windows. if it not works fine we can fix it according the error message

local cmd = 'fennel-ls'
if vim.fn.has('win32') then
  cmd = { 'cmd.exe', '/C', 'fennel-ls'}
end

[gh-liu]

I have tried in wsl2, but it's not work.
The error in lsp.log is .../vim/lsp/rpc.lua:732 "rpc" "cmd.exe" "stderr" "'fennel-ls' is not recognized as an internal or external command,\r\noperable program or batch file.\r\n" , but I do not known how to compile is to a windows EXE file.

[glepnir]

hmmm okay then just need fix the commit message.

[gh-liu]

hmmm okay then just need fix the commit message.

ok

[XeroOl]

The code in server_configurations.md is wrong.

require'lspconfig'.fennel-ls.setup{}    -- wrong
require'lspconfig'['fennel-ls'].setup{} -- fixed