saw two grammatical errors & fixed 'em (#1812)

Author: raidsrc

README.md

@@ -5,7 +5,7 @@
 <br />
 
 <h1 align="center">react-spring</h1>
-<h3 align="center">A spring-physics first animation library <br>giving you flexible tools to confidenty cast your ideas</h3>
+<h3 align="center">A spring-physics first animation library <br>giving you flexible tools to confidently cast your ideas</h3>
 
 <br>
 
@@ -78,7 +78,7 @@ It's as simple as that to create scroll-in animations.
 
 More documentation on the project can be found [here](https://www.react-spring.io).
 
-Pages contain their own [examples](https://react-spring.io/hooks/use-spring#demos) which you can check out there, or [open in codesandbox](https://codesandbox.io/s/github/pmndrs/react-spring/tree/master/demo/src/sandboxes/card) for a more indepth view!
+Pages contain their own [examples](https://react-spring.io/hooks/use-spring#demos) which you can check out there, or [open in codesandbox](https://codesandbox.io/s/github/pmndrs/react-spring/tree/master/demo/src/sandboxes/card) for a more in-depth view!
 
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