doc OOM, log time

README.md

@@ -881,6 +881,15 @@ const coverageOptions = {
 }
 ```
 
+### JavaScript heap out of memory
+When there are a lot of raw v8 coverage files to process, it may cause OOM. We can try the following Node.js options:
+```sh
+- run: npm run test:coverage
+    env:
+        NODE_OPTIONS: --max-old-space-size=8192
+```
+
+
 ## Debug for Coverage and Sourcemap
 > Sometimes, the coverage is not what we expect. The next step is to figure out why, and we can easily find out the answer step by step through debugging.
 - Start debugging for v8 report with option `logging: 'debug'`
@@ -900,6 +909,11 @@ When `logging` is `debug`, the raw report data will be preserved in `[outputDir]
 
 ![](./assets/debug-sourcemap.png)
 
+- Show time logs with env `MCR_LOG_TIME`
+```js
+process.env.MCR_LOG_TIME = true
+```
+
 ## Integration with Any Testing Framework
 - API
     - Collecting coverage data when any stage of the test is completed, and adding the coverage data to the coverage reporter. `await mcr.add(coverageData)`

README.zh-Hans.md

@@ -884,6 +884,15 @@ const coverageOptions = {
 }
 ```
 
+### JavaScript heap out of memory
+内存溢出问题可能出现在有太多的原生V8覆盖率文件要处理. 我们可以使用Node.js的一个选项来增加内存使用:
+```sh
+- run: npm run test:coverage
+    env:
+        NODE_OPTIONS: --max-old-space-size=8192
+```
+
+
 ## Debug for Coverage and Sourcemap
 > 当你觉得覆盖率存在问题的时候，`MCR`支持自行调试来核验覆盖率的准确性
 - 首先打开调试设置`logging: 'debug'`
@@ -903,6 +912,11 @@ const coverageOptions = {
 
 ![](./assets/debug-sourcemap.png)
 
+- 使用环境变量`MCR_LOG_TIME`显示时间日志
+```js
+process.env.MCR_LOG_TIME = true
+```
+
 ## Integration with Any Testing Framework
 通用集成方案
 - 通过API接口在程序集成