.browserslistrc: add `not dead`.
.browserslistrc: add `not dead`.

Hemphill/bootstrap-docs,bardiharborow/bootstrap,stanwmusic/bootstrap,zalog/bootstrap,zalog/bootstrap,coliff/bootstrap,kvlsrg/bootstrap,tagliala/bootstrap,Hemphill/bootstrap-docs,m5o/bootstrap,bootstrapbrasil/bootstrap,GerHobbelt/bootstrap,twbs/bootstrap,kvlsrg/bootstrap,tagliala/bootstrap,stanwmusic/bootstrap,tagliala/bootstrap,nice-fungal/bootstrap,fschumann1211/bootstrap,yuyokk/bootstrap,peterblazejewicz/bootstrap,GerHobbelt/bootstrap,kvlsrg/bootstrap,Hemphill/bootstrap-docs,bootstrapbrasil/bootstrap,fschumann1211/bootstrap,yuyokk/bootstrap,tjkohli/bootstrap,coliff/bootstrap,yuyokk/bootstrap,inway/bootstrap,bardiharborow/bootstrap,bootstrapbrasil/bootstrap,peterblazejewicz/bootstrap,fschumann1211/bootstrap,m5o/bootstrap,bardiharborow/bootstrap,GerHobbelt/bootstrap,fschumann1211/bootstrap,zalog/bootstrap,stanwmusic/bootstrap,yuyokk/bootstrap,gijsbotje/bootstrap,tjkohli/bootstrap,bardiharborow/bootstrap,nice-fungal/bootstrap,twbs/bootstrap,peterblazejewicz/bootstrap,inway/bootstrap,nice-fungal/bootstrap,gijsbotje/bootstrap,gijsbotje/bootstrap,Hemphill/bootstrap-docs,gijsbotje/bootstrap,stanwmusic/bootstrap,inway/bootstrap