How to download and setup linter-xmllint
Open terminal and run command
                                            git clone https://github.com/AtomLinter/linter-xmllint.git
                                        
                                        git clone is used to create a copy or clone of linter-xmllint repositories.
                                        You pass git clone a repository URL. it supports a few different network protocols and corresponding URL formats.
Also you may download zip file with linter-xmllint https://github.com/AtomLinter/linter-xmllint/archive/master.zip
Or simply clone linter-xmllint with SSH
                                            [email protected]:AtomLinter/linter-xmllint.git                                    
                                    If you have some problems with linter-xmllint
You may open issue on linter-xmllint support forum (system) here: https://github.com/AtomLinter/linter-xmllint/issuesSimilar to linter-xmllint repositories
Here you may see linter-xmllint alternatives and analogs
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