docs: add English README

README.en-US.md

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+# XcodeSyncTools
+
+[A English version of this document can be found here](https://github.com/5SMNOONMS5/XcodeSyncTools/blob/master/README_EN.md)
+
+Synchronize built-in **Code-Snippets** and **File-Templates** across different computers in Xcode.
+
+## What are Code-Snippets and File-Templates?
+
+* [How to create Code-Snippets (Tutorial)](Tutorials/README_CS_CN.md)
+
+### Code-Snippets
+
+![](Imgs/git_xcode_sinppets.gif)
+
+* Returns a pre-written snippet based on custom keywords.
+
+### File-Template
+
+* [How to create File-Templates (Tutorial)](Tutorials/README_T_CN.md)
+
+![](Imgs/git_xcode_filetemplate.gif)
+
+* Similar concept to Code-Snippets, but can create pre-defined folder structures.
+
+## Project Workflow
+
+![](Imgs/diagram.png)
+
+* After performing a `git clone` to the local `XcodeSyncTools` directory, running the script will copy the files from the `XcodeSyncTools` directory to `/Users/<YourName>/Library/Developer/Xcode` (hereafter referred to as the Xcode directory). **If** you have [fsevents-tools](https://github.com/ggreer/fsevents-tools) running in the terminal, it will begin **monitoring** file changes in the Xcode directory and sync them back to the `XcodeSyncTools` directory.
+
+* While the primary management is done via git, the main tool being shared here is [fsevents-tools](https://github.com/ggreer/fsevents-tools). `fsevents-tools` utilizes OS X's [FSEvents](https://en.wikipedia.org/wiki/FSEvents) API to monitor changes to files or directories. Whenever any change occurs (add, delete, modify), it will **pipe** the execution to [rsync](https://zh.wikipedia.org/wiki/Rsync) to sync File-Templates and Code-Snippets from the Xcode directory back to the folders under `XcodeSyncTools`. This ensures that whenever a developer modifies template code in Xcode, the files in the `XcodeSyncTools` project change accordingly. Then, git is used to achieve synchronization. You can think of `fsevents-tools` as the OS X version of [inotify](https://zh.wikipedia.org/wiki/Inotify).
+
+## What happens if I don't use this project?
+
+* Nothing at all. Most developers create File-Templates or Code-Snippets directly within Xcode (see the tutorial sections: [Code-Snippets](Tutorials/README_CS_CN.md), [File-Template](Tutorials/README_T_CN.md)). Once created, you usually need to **manually** synchronize them. Using [fsevents-tools](https://github.com/ggreer/fsevents-tools) simply eliminates this manual step.
+
+> You can also pipe the output to any custom script (e.g., executing a githook or `git push`).
+
+## Getting Started
+
+* Clone the project.
+* Run the script to copy files from the `CodeSnippets` and `Templates` folders to the corresponding Xcode directories. (If old versions exist, a backup copy will be created).
+
+* Note: Do not download the project as a ZIP file, as [fsevents-tools](https://github.com/ggreer/fsevents-tools) is added to this project as a [git Submodule](https://git-scm.com/book/en/v2/Git-Tools-Submodule).
+
+```bash
+# Step 1: Clone
+# Via Http
+git clone --depth 1 https://github.com/5SMNOONMS5/XcodeSyncTools.git
+
+# Step 2: Move working directory to XcodeSyncTools
+cd XcodeSyncTools
+
+# Step 3: Sync all files, **only required for the first time**, use -w for monitoring thereafter
+sh xcode-sync.sh -s
+
+# Step 4: Open Xcode and enjoy :)
+```
+
+## More
+
+```bash
+sh xcode-sync.sh -h
+``` 
+
+## Monitoring 
+
+```bash
+sh xcode-sync.sh -w
+``` 
+
+## Having Your Own Code-Snippets and File-Templates
+
+The Code-Snippets and File-Templates in this project are mostly for personal use. If you want to use your own repository, you can modify the `path_source_url` variable inside `xcode-sync.sh`.
+
+![](Imgs/demo_change.png)
+
+After modifying, remember to run:
+
+```bash
+sh xcode-sync.sh -c
+``` 
+
+Then enter the cycle of add, commit, and push to start using your own exclusive Code-Snippets and File-Templates.
+
+## Code-Snippets Keywords
+
+### II
+
+Type **II** (Initialization for most objects)
+
+![](Imgs/demo_ii.png)
+
+### FF
+
+Type **FF** (Custom Swift flag)
+
+![](Imgs/demo_ff.png)
+
+### MM
+
+Type **MM** (Mark)
+
+![](Imgs/demo_mm.png)
+
+### VV
+
+Type **VV** (View lifecycle)
+
+![](Imgs/demo_vv.png)
+
+## How to Use File-Templates
+
+Open Xcode and add a file as usual: File -> New -> File. Scroll to the bottom and you will find them.
+
+![](Imgs/demo_n.png)