Add an .editorconfig file to all SymbiFlow repositories

[mithro]

.editorconfig is a file which tells many editors how to set up their auto formatting configurations. See this example in the Yosys repository -> https://github.com/YosysHQ/yosys/blob/master/.editorconfig

We should create an .editorconfig for SymbiFlow projects and then add it to all our repositories.

We probably need a configurations for;

• [ ] Python files
• [ ] C++ files
• [ ] TCL scripts
• [ ] Bash scripts
• [ ] Makefiles
• [ ] cmake files
• [ ] Verilog files
• [ ] Exclude third_party directory

For Python files, it should match what .yapf settings we are using. For C++ files it should match the Google C++ Style Guide. For Verilog files it should match the LowRISC Verilog Style Guide.

What else have I missed?

[mithro]

; EditorConfig is awesome: http://EditorConfig.org
; At this time of writing, EditorConfig plugins are currently available for:
;
;     Code::Blocks
;     Emacs
;     Geany
;     Gedit
;     jEdit
;     Notepad++
;     Sublime Text 2
;     TextMate
;     Vim
;     Visual Studio

[FFY00]

editorconfig is very limited when it comes to language support, it mostly just allows you to configure the identation and some minor styling preferences.

I think it should be used unless there are better language specific alternatives. Python has flake8, C/C++ has clang-format, I am not sure about the other languages.

[mithro]

@FFY00 - This is more about providing the editor with hints on things like indenting that are consistent with what the formatting tools do. We don't want a person's editor and the code formatting tools fighting.

[FFY00]

Well, flake8 is not really the same thing, but clang-format can be used as a C/C++ specific editorconfig, but yes, it can also be used as a formatter. Anyway, as long as .editorconfig and the language specific tools are in sync there is no issue in providing it, it is still a good addition :)