pkgs(nixvim): Use conform.nvim as formatting plugin, and add two usercmds for it

pkgs/nixvim/formatting.nix

@@ -1,2 +1,102 @@
 {...}: {
+  userCommands = let
+    formatCmd = {
+      desc = "Format all the buffer";
+      # conform.format function can deal with range by itself
+      range = "%";
+      bang = true;
+      bar = true;
+      nargs = "?";
+      complete = {
+        __raw =
+          #lua
+          ''
+            function(ArgLead, CmdLine, CursorPos)
+              return vim.iter(require("conform").list_all_formatters()):filter(function(val)
+                return val.available
+              end):map(function(val)
+                  return val.name
+              end):filter(function(name)
+                return string.match(name, ArgLead) ~= nil
+              end):totable()
+            end
+          '';
+      };
+      command = {
+        __raw =
+          #lua
+          ''
+            function(opts)
+              local format = require("conform").format
+              if #(opts.fargs) == 0 then
+                return format()
+              else
+                return format({ formatters = { opts.fargs[1] } })
+              end
+            end
+          '';
+      };
+    };
+  in {
+    Format = formatCmd;
+    Fmt = formatCmd;
+    Formatter = {
+      desc = "Show config of formatter";
+      nargs = "?";
+      bar = true;
+      complete = {
+        __raw =
+          #lua
+          ''
+            function(ArgLead, CmdLine, CursorPos)
+              return vim.iter(require("conform").list_all_formatters()):map(function(val)
+                return val.name
+              end):filter(function(name)
+                return string.match(name, ArgLead) ~= nil
+              end):totable()
+            end
+          '';
+      };
+      command = {
+        __raw =
+          #lua
+          ''
+            function(opts)
+              local conform = require("conform")
+              if #(opts.fargs) == 0 then
+                local formatters = conform.list_all_formatters()
+                print(vim.inspect(formatters))
+                return formatters
+              else
+                local config = conform.get_formatter_config(opts.fargs[1])
+                print(vim.inspect(config))
+                return config
+              end
+            end
+          '';
+      };
+    };
+  };
+  keymaps = [
+    {
+      action = {
+        __raw =
+          #lua
+          ''
+            function(opts)
+              return require("conform").format()
+            end
+          '';
+      };
+      key = "=";
+      mode = ["n" "v"];
+      options = {
+        desc = "Format with conform";
+      };
+    }
+  ];
+  plugins.conform-nvim = {
+    enable = true;
+    settings.formatters.injected.options.ignore_errors = true;
+  };
 }