Support for Zlint as Zig linter (#4923)

* feat: Add Zig zlint linter and handler for ALE
* docs: Add zlint documentation to ALE Zig integration guide
* docs: Updating docs for zlint support
* tests: Adding tests for checking zlint executable and command
* refactor: Move zlint configuration test to separate test file

test/linter/test_zig_zlint.vader

@@ -0,0 +1,19 @@
+Before:
+  call ale#assert#SetUpLinterTest('zig', 'zlint')
+
+After:
+  call ale#assert#TearDownLinterTest()
+
+Execute(The zlint executable and command should be configured correctly):
+  " Set a custom executable path
+  let g:ale_zig_zlint_executable = '/custom/path/to/zlint'
+
+  " Create a buffer with Zig filetype
+  call ale#test#SetFilename('test.zig')
+
+  " Check the executable
+  AssertEqual '/custom/path/to/zlint', ale#Var(bufnr(''), 'zig_zlint_executable')
+
+  " Check the command
+  let cmd = ale_linters#zig#zlint#GetCommand(bufnr(''))
+  AssertEqual ale#Escape('/custom/path/to/zlint') . ' %s -f gh', cmd