Add link to "BEM SASS" for 'bem-platform' metodology

[SenDen1]

When I implemented 'bem-sass' methodology, I added links to it for all other methodologies at sidebar, except 'bem-platform'. Looks like to implement changes it has to be built. And I'm not sure I would make it correctly. I guess there should be added an object similar to the one for css:

{
    url: 'https://aleshaoleg.github.io/holy-grail-markup/bem-css/',
    content: 'BEM CSS'
},

And command 'node build' run.

[SenDen1]

@tadatuta could you confirm my guesses please, or let me know if I'm mistaken.

[tadatuta]

@SenDen1 yes, looks reasonable

[SenDen1]

@AleshaOleg @ihorzenich Created PR for fixing this issue: https://github.com/AleshaOleg/holy-grail-markup/pull/50

[ihorzenich]

@SenDen1 merged, thanks!