Adding Roc language linters and fixers. (#4966)

* `roc_language_server`

* `roc format`

* `roc format annotate`

test/fixers/test_roc_annotate_fixer_callback.vader

@@ -0,0 +1,20 @@
+Before:
+  call ale#assert#SetUpFixerTest('roc', 'roc_annotate')
+
+After:
+  call ale#assert#TearDownFixerTest()
+
+Execute(The roc annotate callback should return the correct default values):
+  AssertFixer {
+  \    'command': 'roc format annotate %t',
+  \    'read_temporary_file': 1,
+  \}
+
+Execute(The roc annotate callback should allow a custom executable):
+  let g:ale_roc_roc_annotate_executable = 'foo/bar'
+
+  AssertFixer {
+  \    'command': 'foo/bar format annotate %t',
+  \    'read_temporary_file': 1,
+  \}
+

test/fixers/test_roc_format_fixer_callback.vader

@@ -0,0 +1,20 @@
+Before:
+  call ale#assert#SetUpFixerTest('roc', 'roc_format')
+
+After:
+  call ale#assert#TearDownFixerTest()
+
+Execute(The roc format callback should return the correct default values):
+  AssertFixer {
+  \    'command': 'roc format %t',
+  \    'read_temporary_file': 1,
+  \}
+
+Execute(The roc format callback should allow a custom executable):
+  let g:ale_roc_roc_format_executable = 'foo/bar'
+
+  AssertFixer {
+  \    'command': 'foo/bar format %t',
+  \    'read_temporary_file': 1,
+  \}
+

test/linter/test_roc_roc_language_server.vader

@@ -0,0 +1,23 @@
+Before:
+  call ale#assert#SetUpLinterTest('roc', 'roc_language_server')
+
+After:
+  call ale#assert#TearDownLinterTest()
+
+Execute(The default executable path should be correct):
+  AssertLinter 'roc_language_server', ale#Escape('roc_language_server')
+
+Execute(The project root should be detected correctly in empty directory):
+  AssertLSPProject '.'
+
+Execute(The project root should be detected correctly with main.roc):
+  call ale#test#SetFilename('../test-files/roc/main.roc')
+  AssertLSPProject ale#path#Simplify(g:dir . '/../test-files/roc')
+
+Execute(The LSP values should be set correctly):
+  call ale#test#SetFilename('../test-files/roc/main.roc')
+
+  AssertLSPLanguage 'roc'
+  AssertLSPOptions {}
+  AssertLSPConfig {}
+  AssertLSPProject ale#path#Simplify(g:dir . '/../test-files/roc')