Add info about tag replacements

Tool-tasks.md

@@ -24,5 +24,54 @@ Icon         | Category
 ------------ | --------
 :green_book: | Docs/ page generation
 :flashlight: | Verification task
-:pencil2:    | Project file udpate
-:paperclip:  | Technical task
+:pencil2:    | Project file update
+:paperclip:  | Technical task
+
+## Tag replacements
+Markdown pages in the docs/ folder are created based on a template file. This template file may contain tags which are replaced with data during the generation process. For example:
+```txt
+A total of {total} commands are available:
+
+[#commands]
+- {name}[perm], requires {perm}[/perm]
+[/#commands]
+```
+
+Three types of tags are available:
+- Replacement: `{total}`-like tags will be replaced with the value associated with "total"
+- Conditional: `[perm]...[/perm]`-like tags are conditional tags. The text inside of the tags is only considered if the value associated with "perm" is not empty (empty string / empty collection)
+- Repeating: tags like `[#commands]...[/#commands]` will make us iterate over all entries in "commands" and apply replacements to the text within
+
+Values can be associated to tag names with a `TagValueHolder`. Example:
+```java
+List<Command> commands = Arrays.asList(
+  new Command("/home", ""), new Command("/help", "permission.help"));
+
+NestedTagValue commandsInfo = new NestedTagValue();
+for (Command command : commands) {
+  TagValueHolder commandValues = TagValueHolder.create()
+    .put("name", command.getName())
+    .put("permission", command.getPermission());
+  commandsInfo.add(commandValues);
+}
+
+TagValueHolder tagValues = TagValueHolder.create()
+  .put("total", commands.size())
+  .put("commands", commandsInfo);
+
+// Generate MD file
+FileIoUtils.generateFileFromTemplate("commands.tpl.md", "commands.md", tagValues);
+```
+
+The generated file would look like the following:
+```md
+A total of 2 commands are available:
+
+- /home
+- /help, requires permission.help
+```
+
+The following predefined tags are at your disposal:
+- `{gen_date}`: generation date (i.e. current date)
+- `{gen_warning}`: comment warning not to edit the output file directly
+- `{gen_footer}`: info footer with a link to the repo and the generation date