feat: lsp

[dsherret]

Continuation of #741

Seems to work in neovim.

:lua vim.lsp.start({ name='dprint', cmd={'V:\\dprint\\target\\debug\\dprint.exe', 'lsp'} })
:lua vim.lsp.buf.format()

Other helpful neovim commands:

# enable debug logging
:lua vim.lsp.set_log_level('debug')
# get log file name
:lua =require('vim.lsp.log').get_filename()

Todo:

• Schemas for dprint.json files

Closes #738