Bugfix/#967 fish shell support

[Defman21]

Fix #967

I'm no fish shell scripting expert, but it seems to be working:

Running /Users/defman/.vscode/extensions/jakebecker.elixir-ls-0.16.0/elixir-ls-release/launch.sh
Preferred shell is fish, launching launch.fish
Looking for ASDF install
ASDF not found
Looking for rtx executable
rtx executable found in /Users/defman/bin/rtx, activating
Installing ElixirLS release v0.16.0
Running in /Users/defman/.vscode/extensions/jakebecker.elixir-ls-0.16.0/elixir-ls-release
Install complete
[Info  - 11:04:09] Started ElixirLS v0.16.0
[Info  - 11:04:09] Running in /Users/defman/.vscode/extensions/jakebecker.elixir-ls-0.16.0/elixir-ls-release
[Info  - 11:04:09] ElixirLS built with elixir "1.15.4" on OTP "26"
[Info  - 11:04:09] Running on elixir "1.15.4 (compiled with Erlang/OTP 26)" on OTP "26"
[Info  - 11:04:09] Protocols are not consolidated
[Info  - 11:04:09] Elixir sources not found (checking in /home/runner/work/elixir/elixir). Code navigation to Elixir modules disabled.
[Info  - 11:04:09] Received client configuration via workspace/configuration
%{"additionalWatchedExtensions" => [], "autoBuild" => true, "autoInsertRequiredAlias" => true, "dialyzerEnabled" => true, "dialyzerFormat" => "dialyxir_long", "dialyzerWarnOpts" => ["error_handling", "underspecs", "unknown", "unmatched_returns"], "enableTestLenses" => true, "envVariables" => %{}, "fetchDeps" => false, "languageServerOverridePath" => "", "mixEnv" => "test", "mixTarget" => "", "projectDir" => "", "signatureAfterComplete" => true, "suggestSpecs" => true, "trace" => %{"server" => "off"}}
[Info  - 11:04:10] Loaded DETS databases in 118ms
[Info  - 11:04:10] Registering for workspace/didChangeConfiguration notifications
[Info  - 11:04:10] Starting build with MIX_ENV: test MIX_TARGET: host
[Info  - 11:04:10] client/registerCapability succeeded
[Info  - 11:04:10] Registering for workspace/didChangeWatchedFiles notifications
[Info  - 11:04:10] client/registerCapability succeeded
[Info  - 11:04:10] Compile took 165 milliseconds
[Info  - 11:04:10] [ElixirLS WorkspaceSymbols] Indexing...
[Info  - 11:04:10] [ElixirLS Dialyzer] Checking for stale beam files
[Info  - 11:04:10] [ElixirLS WorkspaceSymbols] Module discovery complete
[Info  - 11:04:10] [ElixirLS WorkspaceSymbols] 30 callbacks added to index
[Info  - 11:04:11] [ElixirLS WorkspaceSymbols] 255 modules added to index
[Info  - 11:04:11] [ElixirLS WorkspaceSymbols] 452 types added to index
[Info  - 11:04:12] [ElixirLS Dialyzer] Found 0 changed files in 633 milliseconds
[Info  - 11:04:12] [ElixirLS Dialyzer] Analyzing 0 modules: []
[Info  - 11:04:12] [ElixirLS Dialyzer] Analysis finished in 20 milliseconds
[Info  - 11:04:12] Dialyzer analysis is up to date
[Info  - 11:04:12] [ElixirLS Dialyzer] Writing manifest...
[Info  - 11:04:13] [ElixirLS WorkspaceSymbols] 5038 functions added to index
[Info  - 11:04:13] [ElixirLS Dialyzer] Done writing manifest in 668 milliseconds.

I haven't tested the ELS_ stuff though. If anyone could provide some steps I should perform to test the ELS code, I'd be happy to do them.

[lukaszsamson]

Thanks