Correct the incorrect or not natural English expressions

Thank you for @jonasbn !

.github/CONTRIBUTING.md

@@ -4,24 +4,24 @@ These are the guidelines for contributing to this repository.
 
 ## Issues
 
-Please follow the each template by the type of your issue.
+Please use the template for your type of issue.
 
 - [Bug Report](https://github.com/naokazuterada/MarkdownTOC/issues/new)
 - [Feature Request](https://github.com/naokazuterada/MarkdownTOC/issues/new?template=feature.md)
 - [Question](https://github.com/naokazuterada/MarkdownTOC/issues/new?template=question.md)
 
 ### Way of operation
 
-1. The contributors will `Close` these Issues or PR
+1. The maintainers will `Close` the issue or PR
     1. Not accepted feature request
-        - Add `wontfix` label
-    2. Not obvious and Not responding
-        - Not obvious: Problem is not obvious, or not reproduced.
-        - Not responding: Author doesn't respond in 3 weeks.
+        - Add the `wontfix` label
+    2. Not clear or unresponsive
+        - Not clear: Problem is not obvious or not reproducible.
+        - Unresponsive: the author does not respond to inquiries within 3 weeks.
 
 ## Gitter
 
-If you want to ask more easily, please use [Gitter](https://gitter.im/naokazuterada/MarkdownTOC) chat system.
+If you want more general support or to ask questions, please use [Gitter](https://gitter.im/naokazuterada/MarkdownTOC) chat system.
 
 ## Patches
 
@@ -40,7 +40,7 @@ All contributions are welcome
 
 ## Useful Tools
 
-- [Gyazo](https://gyazo.com/en): Tool for making screen captures into animation GIF. Use it for showing how the function works.
+- [Gyazo](https://gyazo.com/en): Tool for making animated GIFs from screen captures. Use it for showing how the function works.
 
 ## Licensing and copyright
 

.github/ISSUE_TEMPLATE.md

@@ -2,11 +2,11 @@
 
 Template: BUG REPORT
 
-This is an issue for a bug report.
+This is an template for a bug report.
 You should label `bug-report`.
 
 
-If your purpose is different, please visit following links.
+If your issue is not a bug report, please visit one of the following links.
 
 FEATURE REQUEST:
 https://github.com/naokazuterada/MarkdownTOC/issues/new?template=feature.md
@@ -16,10 +16,10 @@ https://github.com/naokazuterada/MarkdownTOC/issues/new?template=question.md
 
 -->
 
-# How can it be reproduced
+# How can the issue be reproduced
 
 # What was expected
 
 # What actually occurred
 
-# What version of the involved component
+# What was the version of the involved component

.github/ISSUE_TEMPLATE/feature.md

@@ -2,11 +2,11 @@
 
 Template: FEATURE REQUEST
 
-This is an issue for a feature request.
+This is an template for a feature request.
 You should label `feature-request`.
 
 
-If your purpose is different, please visit following links.
+If your issue is not a feature request, please visit one of the following links.
 
 BUG REPORT:
 https://github.com/naokazuterada/MarkdownTOC/issues/new?template=bug.md

.github/ISSUE_TEMPLATE/question.md

@@ -2,11 +2,11 @@
 
 Template: QUESTION
 
-This is an issue for a feature request.
+This is a template for a general question
 You should label `question`.
 
 
-If your purpose is different, please visit following links.
+If your issue is not a question, please visit one of the following links.
 
 BUG REPORT:
 https://github.com/naokazuterada/MarkdownTOC/issues/new?template=bug.md