README: add setup instruction

Signed-off-by: Tianling Shen <[email protected]>

README.md

@@ -1 +1,50 @@
-# helloworld
+## Setup instruction
+
+### Method 1 - Add this repo as a git submodule
+
+- Add new submodule:
+
+  ```bash
+  git submodule add --name helloworld https://github.com/fw876/helloworld.git package/helloworld
+  ```
+
+- Pull upstream commits:
+
+  ```bash
+  git submodule update --remote package/helloworld
+  ```
+
+### Method 2 - Add this repo as an OpenWrt feed
+
+- Add new feed:
+
+  ```bash
+  sed -i "/helloworld/d" "feeds.conf.default"
+  echo "src-git helloworld https://github.com/fw876/helloworld.git" >> "feeds.conf.default"
+  ```
+
+- Pull upstream commits:
+
+  ```bash
+  ./scripts/feeds update helloworld
+  ./scripts/feeds install -a -f -p helloworld
+  ```
+
+### Notice
+
+If you want to use this repo with official OpenWrt source tree, the following packages need to be added manually:
+
+- [dns2socks](https://github.com/immortalwrt/packages/tree/master/net/dns2socks)
+- [microsocks](https://github.com/immortalwrt/packages/tree/master/net/microsocks)
+- [ipt2socks](https://github.com/immortalwrt/packages/tree/master/net/ipt2socks)
+- [pdnsd-alt](https://github.com/immortalwrt/packages/tree/master/net/pdnsd-alt)
+- [redsocks2](https://github.com/immortalwrt/packages/tree/master/net/redsocks2)
+
+You may use `svn` to check them out, e.g.:
+
+```bash
+mkdir -p package/helloworld
+for i in "dns2socks" "microsocks" "ipt2socks" "pdnsd-alt" "redsocks2"; do \
+  svn checkout "https://github.com/immortalwrt/packages/trunk/net/$i" "package/helloworld/$i"; \
+done
+```