Update installation instructions
Update installation instructions

-Fix grammar
-Add SELinux section

pmichelazzo/wallabag,pmichelazzo/wallabag,pmichelazzo/wallabag,X-dark/wallabag,egilli/wallabag,egilli/wallabag,wallabag/wallabag,egilli/wallabag,shtrom/wallabag,pmichelazzo/wallabag,X-dark/wallabag,wallabag/wallabag,X-dark/wallabag,egilli/wallabag,shtrom/wallabag,X-dark/wallabag,wallabag/wallabag,shtrom/wallabag,pmichelazzo/wallabag,egilli/wallabag,shtrom/wallabag,X-dark/wallabag,shtrom/wallabag