Add Erlang Language Server

[S0AndS0]

Initial tests, after satisfying dependencies, seem to show a good time can be had between YouCompleteMe and Erlang Language Server!

YCM log snippet

127.0.0.1 - - [21/Jan/2025 15:40:36] "POST /debug_info HTTP/1.1" 200 332
2025-01-21 15:40:59,510 - INFO - Initializing generic LSP completer with: {'project_root_files': ['erlang_ls.config', 'erlang_ls.yaml'], 'name': 'erlang', 'cmdline': ['~/git/hub/ycm-core/lsp-examples/erlang/erlang_ls/_build/default/bin/erlang_ls', '--transport', 'stdio'], 'filetypes': ['erlang']}
2025-01-21 15:40:59,510 - INFO - Completion config: 50, detailing 0 candiates
127.0.0.1 - - [21/Jan/2025 15:40:59] "GET /signature_help_available?subserver=erlang HTTP/1.1" 200 23
2025-01-21 15:40:59,594 - DEBUG - Event name: BufferVisit
127.0.0.1 - - [21/Jan/2025 15:40:59] "POST /event_notification HTTP/1.1" 200 2
2025-01-21 15:40:59,597 - DEBUG - Event name: FileReadyToParse
2025-01-21 15:40:59,597 - INFO - Adding buffer identifiers for file: /tmp/test.erl

Good code produces no warnings or errors via YCM;

-module(test).

-export([testy/0]).
testy() -> true.

Questionable code produces warnings;

-module(test).

questionable_idea() -> 'wat'.

/tmp/test.erl|3 col 1 warning| function questionable_idea/0 is unused

Bad code pops the errors;

-module(test).

-export([bad_idea/0]).
bad_idea() -> 1 - Nan.

/tmp/test.erl|4 col 19 error| variable 'Nan' is unbound

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