doc: use absolute links in style guide, add link to cookiecutter

doc/development/style_guide.md

@@ -52,10 +52,10 @@ Use Flake8 to check formatting and basic issues in all files:
 flake8 python_file.py
 ```
 
-The root directory contains [.flake8](../../.flake8) configuration file which
-contains a less strict configuration for legacy code. It will be used by default
-when running Flake8 within GRASS source code. For new files, you can use the
-default configuration:
+The root directory contains [.flake8](https://github.com/OSGeo/grass/blob/main/.flake8)
+configuration file which contains a less strict configuration for legacy code.
+It will be used by default when running Flake8 within GRASS source code.
+For new files, you can use the default configuration:
 
 ```bash
 flake8 --isolated --max-line-length=88 {path_to_python_file}
@@ -83,11 +83,11 @@ clang-format -i <new_or_modified_file.c>
 ```
 
 The ClangFormat settings for the repo are defined in
-[.clang-format](../../.clang-format).
+[.clang-format](https://github.com/OSGeo/grass/blob/main/.clang-format).
 
 If using pre-commit is not an option, for whatever reason, there is a helper
-script [grass_clang_format.sh](./utils/grass_clang_format.sh), which simplifies
-bulk reformatting.
+script [grass_clang_format.sh](https://github.com/OSGeo/grass/blob/main/utils/grass_clang_format.sh),
+which simplifies bulk reformatting.
 
 #### Order of include headers
 
@@ -166,7 +166,7 @@ pre-commit run --files raster/r.sometool/*
 ```
 
 The pre-commit hooks set is defined in
-[.pre-commit-config.yaml](../../.pre-commit-config.yaml).
+[.pre-commit-config.yaml](https://github.com/OSGeo/grass/blob/main/.pre-commit-config.yaml).
 
 It is possible to temporally disable the pre-commit hooks in the repo, e.g. while
 working on older branches:
@@ -880,7 +880,7 @@ These index manual pages are autogenerated during the build process of GRASS.
 
 #### Lazy import of optional dependencies
 
-A tool may use a package that is not [required](../../REQUIREMENTS.md)
+A tool may use a package that is not [required](https://github.com/OSGeo/grass/blob/main/REQUIREMENTS.md)
 by GRASS and may not be available on a user's system.
 In these cases, import only after the _gs.parser_ call. In that way the
 tool can be safely compiled even if the dependency is not installed.

man/mkdocs/docs/development_intro.md

@@ -26,6 +26,7 @@ The addons are maintained by the GRASS community and are a great way to extend t
 functionality of GRASS.
 
 - [Addons](https://grass.osgeo.org/grass-stable/manuals/addons/)
+- [Template for addons](https://github.com/OSGeo/grass-addon-cookiecutter)
 
 ## Contributing