Add minimum version to build docs support

Author: halx99

README.md

@@ -103,6 +103,7 @@ Some highlights:
 - **Universal Windows Platform** (UWP) support for Xbox consoles
 - **Apple M1 and Android x64 support** (by @pietpukkel)
 - **Windows x64 build support**
+- **Powerful cross-platform build system**
 - Improved Windows workflow, supporting linking with engine prebuilt libs. Please read the [Windows workflow guide](https://github.com/axmolengine/axmol/issues/564).
 - Refactored AudioEngine, OpenAL for all platforms:
     - [OpenAL Soft](https://github.com/kcat/openal-soft) (pass `-DAX_USE_ALSOFT=ON` to CMake to force enabling it)

README_CN.md

@@ -111,6 +111,7 @@ Axmol 引擎在 Cocos2d-x v4.0 的基础上进行迭代和改进。现在速度
 - **Apple M1 和 Android x64 支持** (by @pietpukkel)。
 - **Windows x64 构建支持**。
 - **Windows SIMD 加速指令矩阵计算支持**。
+- **强大的跨平台构建系统**。
 - 支持链接引擎预编译库。 详见 [Windows 工作流指导](https://github.com/axmolengine/axmol/issues/564)。
 - 重构 AudioEngine，所有平台均使用 OpenAL 并新增 `.wav` 音频格式支持。
 - 使用内存映射文件 [mio](https://github.com/mandreyel/mio) 重构 UserDefault，速度提升百倍。 

tools/ci/build-docs.ps1

@@ -1,7 +1,8 @@
 
 # Can runs on Windows,Linux
 param(
-    $site_dist = $null
+    $site_dist = $null,
+    $min_ver = '2.3' # The minimum version to build docs
 )
 
 $myRoot = $PSScriptRoot
@@ -123,16 +124,23 @@ function  configure_file($infile, $outfile, $vars) {
 
 # query version map to build docs
 $release_tags = $(git tag)
-$verMap = @{'latest' = $null; }
+$verMap = @{}
 foreach ($item in $release_tags) {
     if ([Regex]::Match($item, '^v[0-9]+\.[0-9]+\.[0-9]+$').Success) {
         $docVer = $($item.Split('.')[0..1] -join '.').TrimStart('v')
+        if ($docVer -lt $min_ver) {
+            continue
+        }
         $verMap[$docVer] = $item
     }
 }
-$strVerList = "'$($verMap.Keys -join "','")'"
-Write-Host "$(Out-String -InputObject $verMap)"
 
+$verList = $verMap.GetEnumerator() | Sort-Object Value -Descending | ForEach-Object { $_.Key }
+
+$verMap['latest'] = $null
+
+$strVerList = "'latest','$($verList -join "','")'"
+Write-Host "$(Out-String -InputObject $verMap)"
 
 # set default doc ver to 'latest'
 mkdirs "$site_dist/manual"