[GH-19267] Spelling comments (#19268)

* spelling: comments

Signed-off-by: Josh Soref <jsoref@users.noreply.github.com>
Co-authored-by: Josh Soref <jsoref@users.noreply.github.com>
Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

tests/README.md

@@ -19,9 +19,9 @@ It is possible to manually test specific sections of any test, instead of using
 
 ## Test plugins
 
-There are two test plugins: `testplugin.tar.gz` and `testplugin2.tar.gz`. These are use in some integration tests in the `api4` package. Any changes to the plugin bundles require updating the coresponding signatures.
+There are two test plugins: `testplugin.tar.gz` and `testplugin2.tar.gz`. These are use in some integration tests in the `api4` package. Any changes to the plugin bundles require updating the corresponding signatures.
 
-First, import the public and privat development key:
+First, import the public and private development key:
 ```
 $ gpg --import ./development-public-key.gpg
 $ gpg --import ./development-private-key.asc
@@ -29,7 +29,7 @@ $ gpg --import ./development-private-key.asc
 
 This has to be done only once.
 
-Then update the sigantures:
+Then update the signatures:
 ```
 $ gpg -u F3FACE45E0DE642C8BD6A8E64C7C6562C192CC1F --verbose --personal-digest-preferences SHA256 --detach-sign testplugin.tar.gz
 $ gpg -u F3FACE45E0DE642C8BD6A8E64C7C6562C192CC1F --verbose --personal-digest-preferences SHA256 --detach-sign --armor testplugin.tar.gz

tests/test-markdown-basics.md

@@ -55,7 +55,7 @@ _Italics_
 - List
   - List Sub-item
 [Link](http://i.giphy.com/xNrM4cGJ8u3ao.gif)
-[![Github](https://assets-cdn.github.com/favicon.ico)](https://github.com/mattermost/platform)
+[![GitHub](https://assets-cdn.github.com/favicon.ico)](https://github.com/mattermost/platform)
 | Left-Aligned Text | Center Aligned Text | Right Aligned Text |
 | :------------ |:---------------:| -----:|
 | Left column 1 | this text       |  $100 |