docs: move Programmer's manual creation to INSTALL.md (#4336)

- move Programmer's manual creation from `doc/development/README.md` to `INSTALL.md`.

update `doc/development/README.md`
- add Python API; add subsections
- update URLs and wording
- list guides

- remove stray control chars (visible in vim) in `doc/development/style_guide.md`

INSTALL.md

@@ -321,9 +321,35 @@ developers mailing list. See <https://grass.osgeo.org/development/>
 
 ## (L) GRASS PROGRAMMER'S MANUAL
 
-The Programmer's manual is generated with doxygen from the source code.
-Please see the [README](doc/development/README.md) file and the files at:
-<https://grass.osgeo.org/programming8/>
+The Programmer's manual <https://grass.osgeo.org/programming8/> is
+generated from the source code. This requires the installation of
+`doxygen` (<http://www.doxygen.nl>) and optionally Graphviz `dot`
+(<https://graphviz.org/doc/info/command.html>).
+
+The main file is: `./grasslib.dox` where all sub-documents have
+to be linked to.
+
+To locally generate the 'Programmer's Manual', run
+
+```sh
+make htmldocs
+```
+
+To generate documentation as a single html file
+(recommended for simple reading)
+
+```sh
+make htmldocs-single
+```
+
+This process takes some time. The result will be found in
+the file `lib/html/index.html`.
+
+To generate the 'Programmer's Manual' in PDF format, run
+
+```sh
+make pdfdocs
+```
 
 ## (M) CONTRIBUTING CODE AND PATCHES
 

doc/development/README.md

@@ -1,43 +1,19 @@
 # Development and Maintenance Documentation
 
-Here is development and maitanance documentation. The API documentation
-is at appropriate places, but here is the information relevant to
-contributing to GRASS GIS and its maintanance.
+Find below the development and maintenance documentation.
+The API documentation is available in the appropriate places,
+but here is the information relevant to contributing to and
+maintaining GRASS GIS.
 
-## How to generate the 'Programmer's Manual'
+## Style and GitHub guide
 
-You can locally generate the [GRASS GIS Programmer's Manual](https://grass.osgeo.org/programming8/).
+- [GRASS Programming Style Guide](style_guide.md)
+- [Guide to contributing on GitHub](github_guide.md)
 
-This needs doxygen (<http://www.doxygen.org>) and optionally
-Graphviz dot (<http://www.research.att.com/sw/tools/graphviz/>).
+## Python API
 
-To build the GRASS programmer's documentation, run
+- ["grass" Python package documentation](https://grass.osgeo.org/grass-devel/manuals/libpython/)
 
-```sh
-make htmldocs
-```
+## C API
 
-Or to generate documentation as a single html file
-(recommended for simple reading)
-
-```sh
-make htmldocs-single
-```
-
-This takes quite some time. The result is in `lib/html/index.html`
-which refers to further document repositories in
-
-```text
-lib/vector/html/index.html
-lib/db/html/index.html
-lib/gis/html/index.html
-```
-
-The master file is: `./grasslib.dox` where all sub-documents have to
-be linked to.
-
-To generate the documents in PDF format, run
-
-```sh
-make pdfdocs
-```
+- [GRASS Programmer's manual](https://grass.osgeo.org/programming8/)

doc/development/style_guide.md

@@ -122,7 +122,7 @@ sorted and separated by a newline.
 
 Use function names which fulfill the official [GNU naming
 convention](https://www.gnu.org/prep/standards/html_node/Names.html). Instead of
-naming a function like: MyNewFunction() use snake case: my_new_function()`.
+naming a function like: `MyNewFunction()` use snake case: `my_new_function()`.
 
 ### Using pre-commit
 
@@ -192,7 +192,7 @@ There are three types of documentation: C API, Python API and tool documentation
 #### C API documentation
 
 We
-[​use doxygen and document the functions](https://grass.osgeo.org/programming8/)
+[use doxygen and document the functions](https://grass.osgeo.org/programming8/)
 directly in the source code. See `lib/gis/open.c` and `lib/gis/gislib.dox` for
 examples.
 
@@ -947,7 +947,7 @@ gs.message(_("Running through {}").format(shellname))
 ### Developing C tools
 
 Refer to the [online GRASS Programmer's
-Manual](​https://grass.osgeo.org/programming8/) or generate it with `make
+Manual](https://grass.osgeo.org/programming8/) or generate it with `make
 htmldocs` or `make pdfdocs`.
 
 #### Use GRASS library functions
@@ -962,7 +962,7 @@ improves portability.
 - File seek: `G_fseek()`, `G_ftell()`
 - Printing: `G_asprintf()`, `G_vsaprintf()`, `G_vfaprintf()`, ...
 
-Please refer to [the programmers manual](https://grass.osgeo.org/programming8/)
+Please refer to the [programmers manual](https://grass.osgeo.org/programming8/)
 for the proper use (e.g., determining if any casts are needed for arguments or
 return values) of these library functions. They may perform a task slightly
 different from their corresponding C library function, and thus, their use may