add dash symbols as separator

content/docs/how-to-contribute.md

@@ -146,11 +146,11 @@ However, there are still some styles that the linter cannot pick up. If you are
 You may be interested in watching [this short video](https://www.youtube.com/watch?v=wUpPsEcGsg8) (26 mins) which gives an introduction on how to contribute to React.
 
 #### Video highlights:
-- [4:12](https://youtu.be/wUpPsEcGsg8?t=4m12s) Building and testing React locally
-- [6:07](https://youtu.be/wUpPsEcGsg8?t=6m7s) Creating and sending pull requests
-- [8:25](https://youtu.be/wUpPsEcGsg8?t=8m25s) Organizing code
-- [14:43](https://youtu.be/wUpPsEcGsg8?t=14m43s) React npm registry
-- [19:15](https://youtu.be/wUpPsEcGsg8?t=19m15s) Adding new React features
+- [4:12](https://youtu.be/wUpPsEcGsg8?t=4m12s) - Building and testing React locally
+- [6:07](https://youtu.be/wUpPsEcGsg8?t=6m7s) - Creating and sending pull requests
+- [8:25](https://youtu.be/wUpPsEcGsg8?t=8m25s) - Organizing code
+- [14:43](https://youtu.be/wUpPsEcGsg8?t=14m43s) - React npm registry
+- [19:15](https://youtu.be/wUpPsEcGsg8?t=19m15s) - Adding new React features
 
 ### Meeting Notes