Fix typos in docs

Closes #2150

docs/CONTRIBUTING.md

@@ -351,8 +351,8 @@ __Note:__ If you haven't already implemented the feature, check first if there
 already is an open issue for it and if it's already being developed in an
 [experimental branch](https://github.com/glfw/glfw/branches/all).
 
-__There is no preferred patch size__.  A one character change is just as welcome
-as one adding a thousand line one, if that is the appropriate size for the
+__There is no preferred patch size__.  A one-character change is just as welcome
+as one adding a thousand lines, if that is the appropriate size for the
 feature.
 
 In addition to the code, a complete feature includes:

docs/build.dox

@@ -57,7 +57,7 @@ macros that disable similar headers below it.
 
 Both of these mechanisms depend on the extension loader header defining a known
 macro.  If yours doesn't or you don't know which one your users will pick, the
-@ref GLFW_INCLUDE_NONE macro will explicitly to prevent the GLFW header from
+@ref GLFW_INCLUDE_NONE macro will explicitly prevent the GLFW header from
 including the OpenGL header.  This will also allow you to include the two
 headers in any order.