add: Arc browser support.

README.md

@@ -2,7 +2,7 @@
 
 Turn your browser¹ into a Neovim client (demos: [justinmk 🇺🇸](https://www.youtube.com/watch?v=suvh0yFfIB8), [Sean Feng 🇨🇳](https://www.youtube.com/watch?v=dNQJONKnJrg)).
 
-¹ <sub>Firefox and Chrome are specifically supported. Other Chromium based browsers such as Brave, Vivaldi, and Opera should also work but are not specifically tested.</sub>
+¹ <sub>Firefox and Chrome are specifically supported. Other Chromium based browsers such as Brave, Vivaldi, Opera, and Arc should also work but are not specifically tested.</sub>
 
 ![Firenvim demo](firenvim.gif)
 
@@ -77,7 +77,7 @@ If you would rather build and install Firenvim from source, check [CONTRIBUTING.
 
 #### Other browsers
 
-Other browsers aren't supported for now. Opera, Vivaldi and other Chromium-based browsers should however work just like in Chromium and have similar install steps. Brave and Edge might work, Safari doesn't (it doesn't support Webextensions).
+Other browsers aren't supported for now. Opera, Vivaldi and other Chromium-based browsers should however work just like in Chromium and have similar install steps. Brave, Edge, and Arc might work, Safari doesn't (it doesn't support Webextensions).
 
 ## Permissions
 

autoload/firenvim.vim

@@ -309,6 +309,14 @@ function! s:get_librewolf_manifest_dir_path() abort
         return s:build_path([$HOME, '.librewolf', 'native-messaging-hosts'])
 endfunction
 
+function! s:arc_config_exists() abort
+        let l:p = [$HOME, '.config', 'Arc']
+        if has('mac')
+                let l:p = [$HOME, 'Library', 'Application Support', 'Arc']
+        end
+        return isdirectory(s:build_path(l:p))
+endfunction
+
 function! s:brave_config_exists() abort
         let l:p = [$HOME, '.config', 'BraveSoftware']
         if has('mac')
@@ -464,6 +472,13 @@ function! s:get_chrome_dev_manifest_dir_path() abort
         return s:build_path([$HOME, '.config', 'google-chrome-unstable', 'NativeMessagingHosts'])
 endfunction
 
+function! s:get_arc_manifest_dir_path() abort
+        if has('mac')
+                return s:get_chrome_manifest_dir_path()
+        end
+        return throw 'No Arc on any other than mac.'
+endfunction
+
 function! s:get_brave_manifest_dir_path() abort
         if has('mac')
                 return s:get_chrome_manifest_dir_path()
@@ -694,6 +709,12 @@ endfunction
 function! s:get_browser_configuration() abort
         " Brave, Opera and Vivaldi all rely on Chrome's native messenger
         let l:browsers = {
+                \'arc': {
+                        \ 'has_config': s:arc_config_exists(),
+                        \ 'manifest_content': function('s:get_chrome_manifest'),
+                        \ 'manifest_dir_path': function('s:get_arc_manifest_dir_path'),
+                        \ 'registry_key': 'HKCU:\Software\Google\Chrome\NativeMessagingHosts\firenvim',
+                \},
                 \'brave': {
                         \ 'has_config': s:brave_config_exists(),
                         \ 'manifest_content': function('s:get_chrome_manifest'),