docs: update build docs,support Powershell on Windows (#41882)

* docs: update build docs,support Powershell on Windows

Co-authored-by: nashaofu <diaocheng@outlook.com>

* chore: fix capitalization

Co-authored-by: nashaofu <diaocheng@outlook.com>

---------

Co-authored-by: trop[bot] <37223003+trop[bot]@users.noreply.github.com>
Co-authored-by: nashaofu <diaocheng@outlook.com>

docs/development/build-instructions-gn.md

@@ -110,22 +110,51 @@ $ export CHROMIUM_BUILDTOOLS_PATH=`pwd`/buildtools
 On Windows:
 
 ```sh
+# cmd
 $ cd src
 $ set CHROMIUM_BUILDTOOLS_PATH=%cd%\buildtools
+
+# PowerShell
+$ cd src
+$ $env:CHROMIUM_BUILDTOOLS_PATH = "$(Get-Location)\buildtools"
 ```
 
 **To generate Testing build config of Electron:**
 
+On Linux & MacOS
+
 ```sh
 $ gn gen out/Testing --args="import(\"//electron/build/args/testing.gn\")"
 ```
 
+On Windows:
+
+```sh
+# cmd
+$ gn gen out/Testing --args="import(\"//electron/build/args/testing.gn\")"
+
+# PowerShell
+gn gen out/Testing --args="import(\`"//electron/build/args/testing.gn\`")"
+```
+
 **To generate Release build config of Electron:**
 
+On Linux & MacOS
+
 ```sh
 $ gn gen out/Release --args="import(\"//electron/build/args/release.gn\")"
 ```
 
+On Windows:
+
+```sh
+# cmd
+$ gn gen out/Release --args="import(\"//electron/build/args/release.gn\")"
+
+# PowerShell
+$ gn gen out/Release --args="import(\`"//electron/build/args/release.gn\`")"
+```
+
 **Note:** This will generate a `out/Testing` or `out/Release` build directory under `src/` with the testing or release build depending upon the configuration passed above. You can replace `Testing|Release` with another names, but it should be a subdirectory of `out`.
 
 Also you shouldn't have to run `gn gen` again—if you want to change the build arguments, you can run `gn args out/Testing` to bring up an editor. To see the list of available build configuration options, run `gn args out/Testing --list`.