Add naga linter for WGSL support (#4047)

* Add WGSL support using `naga` command

* Add documents for wgsl

* Add test for `naga` linter

* Separate naga handler callback to hanlder/naga.vim

ale_linters/wgsl/naga.vim

@@ -0,0 +1,12 @@
+" Author: rhysd <https://github.com/rhysd>
+" Description: naga-cli linter for WGSL syntax.
+
+call ale#Set('wgsl_naga_executable', 'naga')
+
+call ale#linter#Define('wgsl', {
+\   'name': 'naga',
+\   'executable': {b -> ale#Var(b, 'wgsl_naga_executable')},
+\   'output_stream': 'stderr',
+\   'command': {b -> '%e --stdin-file-path %s'},
+\   'callback': 'ale#handlers#naga#Handle',
+\})