fix some typos

CONTRIBUTING.md

@@ -83,7 +83,7 @@ history when coming from PRs.
 Also try to make commits that bring the engine from one stable state to another
 stable state, i.e. if your first commit has a bug that you fixed in the second
 commit, try to merge them together before making your pull request (see ``git
-rebase -i`` and relevant help about rebasing or ammending commits on the
+rebase -i`` and relevant help about rebasing or amending commits on the
 Internet).
 
 This git style guide has some good practices to have in mind:

thirdparty/README.md

@@ -57,7 +57,7 @@ Files extracted from upstream source:
 - Version: 1.06
 - License: OFL-1.1
 
-Use UI font if exists, because it has tight vertial metrix and good for UI.
+Use UI font if exists, because it has tight vertical metrics and good for UI.
 
 ### Hack Regular
 
@@ -239,7 +239,7 @@ Collection of single-file libraries used in Godot components.
   * License: RSA Message-Digest License
 - `pcg.{cpp,h}`
   * Upstream: http://www.pcg-random.org
-  * Version: minimal C implemention, http://www.pcg-random.org/download.html
+  * Version: minimal C implementation, http://www.pcg-random.org/download.html
   * License: Apache 2.0
 - `sha256.{c,h}`
   * Upstream: https://github.com/ilvn/SHA256