README: add

README.md

@@ -0,0 +1,69 @@
+pbvm
+====
+
+pbvm - Protocol Buffers Version Manager.
+
+Install
+=======
+
+```sh
+# download & unpack
+$ wget https://github.com/ekalinin/pbvm/releases/download/0.0.1/pbvm.linux.amd64.tgz
+$ tar xzvf pbvm.linux.amd64.tgz
+
+# install
+$ chmod +x pbvm
+$ sudo cp pbvm /usr/bin
+
+# activate
+$ export PATH="$PATH:$HOME/.pbvm/active/bin"
+```
+
+Usage
+=====
+
+List available versions
+-----------------------
+
+```sh
+$ pbvm list-remote -n 5     
+   VERSION   | PRE-RELEASE |    DATE    | INSTALLED  
+-------------+-------------+------------+------------
+  v4.0.0-rc1 | true        | 2020.07.15 | true       
+  v3.12.3    | false       | 2020.06.03 | true       
+  v3.12.2    | false       | 2020.05.26 | false      
+  v3.12.1    | false       | 2020.05.20 | false      
+  v3.12.0    | false       | 2020.05.15 | true 
+```
+
+Install (switch) to version
+----------------------------
+
+```sh
+$ pbvm install v4.0.0-rc1
+$ protoc --version
+libprotoc 4.0.0
+
+$ pbvm install v3.12.3
+$ protoc --version
+libprotoc 3.12.3
+
+# will just switch active version (without downloading)
+$ pbvm install v4.0.0-rc1
+$ protoc --version
+libprotoc 3.12.3
+```
+
+Run with a version
+------------------
+
+```sh
+$ protoc --version
+libprotoc 3.12.3
+
+$ pbvm run "protoc --version" --version v4.0.0-rc1        
+libprotoc 4.0.0
+
+$ protoc --version
+libprotoc 3.12.3
+```