docs: Update various links from old 'gh-pages' branch to 'main'.

This will make Obsidian Plugins Browser show the latest Tasks screenshots.

README.md

@@ -19,16 +19,16 @@ For changes in each release, please check the releases page: <https://github.com
 - _All screenshots assume the [global filter](https://publish.obsidian.md/tasks/Getting+Started/Global+Filter) `#task` which is not set by default (see also [installation](https://publish.obsidian.md/tasks/Installation/Installation))._
 - _The theme is default Obsidian theme._
 
-![ACME Tasks](https://github.com/obsidian-tasks-group/obsidian-tasks/raw/gh-pages/docs/images/acme.png)
+![ACME Tasks](https://github.com/obsidian-tasks-group/obsidian-tasks/raw/main/docs/images/acme.png)
 The `ACME` note has some tasks.
 
-![Important Project Tasks](https://github.com/obsidian-tasks-group/obsidian-tasks/raw/gh-pages/docs/images/important_project.png)
+![Important Project Tasks](https://github.com/obsidian-tasks-group/obsidian-tasks/raw/main/docs/images/important_project.png)
 The `Important Project` note also has some tasks.
 
-![Tasks Queries](https://github.com/obsidian-tasks-group/obsidian-tasks/raw/gh-pages/docs/images/tasks_queries.png)
+![Tasks Queries](https://github.com/obsidian-tasks-group/obsidian-tasks/raw/main/docs/images/tasks_queries.png)
 The `Tasks` note gathers all tasks from the vault and displays them using queries.
 
-![Create or Edit Modal](https://github.com/obsidian-tasks-group/obsidian-tasks/raw/gh-pages/docs/images/modal.png)
+![Create or Edit Modal](https://github.com/obsidian-tasks-group/obsidian-tasks/raw/main/docs/images/modal.png)
 The `Tasks: Create or edit` command helps you when editing a task.
 
 ## Installation

docs/How To/How to style backlinks.md

@@ -39,7 +39,7 @@ We could also use `short mode`, which would replace the backlink text with an ic
 
 ## Using CSS to de-emphasize the backlinks
 
-We can de-emphasize the text in the backlinks, with [this CSS snippet](https://github.com/obsidian-tasks-group/obsidian-tasks/blob/gh-pages/resources/sample_vaults/Tasks-Demo/.obsidian/snippets/tasks-plugin-backlinks-small-grey.css):
+We can de-emphasize the text in the backlinks, with [this CSS snippet](https://github.com/obsidian-tasks-group/obsidian-tasks/blob/main/resources/sample_vaults/Tasks-Demo/.obsidian/snippets/tasks-plugin-backlinks-small-grey.css):
 
 <!-- snippet: resources/sample_vaults/Tasks-Demo/.obsidian/snippets/tasks-plugin-backlinks-small-grey.css -->
 ```css
@@ -60,7 +60,7 @@ Which gives us this result:
 
 ## Using CSS to replace the backlinks with icons
 
-Or we can replace the backlink text with an icon, with [this CSS snippet](https://github.com/obsidian-tasks-group/obsidian-tasks/blob/gh-pages/resources/sample_vaults/Tasks-Demo/.obsidian/snippets/tasks-plugin-backlinks-icon.css):
+Or we can replace the backlink text with an icon, with [this CSS snippet](https://github.com/obsidian-tasks-group/obsidian-tasks/blob/main/resources/sample_vaults/Tasks-Demo/.obsidian/snippets/tasks-plugin-backlinks-icon.css):
 
 <!-- snippet: resources/sample_vaults/Tasks-Demo/.obsidian/snippets/tasks-plugin-backlinks-icon.css -->
 ```css

docs/Queries/Explaining Queries.md

@@ -255,7 +255,7 @@ Explanation of this Tasks code block query:
 
   filename includes file path.md
 
-  description includes Some Cryptic String 
+  description includes Some Cryptic String
 
   No grouping instructions supplied.
 
@@ -273,7 +273,7 @@ For readability, explanations are shown in a fixed-width font (a `PRE` block), a
 
 Using a [CSS snippet in Obsidian](https://help.obsidian.md/How+to/Add+custom+styles#Use+Themes+and+or+CSS+snippets), we can change the appearance of the explanation block.
 
-For example, [this CSS snippet](https://github.com/obsidian-tasks-group/obsidian-tasks/blob/gh-pages/resources/sample_vaults/Tasks-Demo/.obsidian/snippets/tasks-plugin-explain-text-blue.css) `tasks-plugin-explain-text-blue.css` makes the explanation block text blue:
+For example, [this CSS snippet](https://github.com/obsidian-tasks-group/obsidian-tasks/blob/main/resources/sample_vaults/Tasks-Demo/.obsidian/snippets/tasks-plugin-explain-text-blue.css) `tasks-plugin-explain-text-blue.css` makes the explanation block text blue:
 
 <!-- snippet: resources/sample_vaults/Tasks-Demo/.obsidian/snippets/tasks-plugin-explain-text-blue.css -->
 ```css