[core] Add fontWeightBold as 700(default)

[aditya1906]

Closes #15801

[mui-pr-bot]

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Comparing: 21582fd...f39c477

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Generated by 🚫 dangerJS against f39c477

[aditya1906]

The failure is because I changed 600 to Strong and added fontWeightBold wherever necessary. Otherwise I think it is much better to use this way of define fontWeights.

[aditya1906]

@eps1lon what are your thoughts on this PR?

[oliviertassinari]

@aditya1906 It's a great start! I have tried to push it one step further. Let me push the changes. Unfortunately, I can't do it here as you have removed the remote branch:

Let's continue the changes in #16036. This initial effort was continued in #16038 by @merceyz. It supersedes the initial request. Instead, we can recycle the remote branch :).

[aditya1906]

Okay @oliviertassinari surely We can do that

[aditya1906]

I'm extremely sorry that I accidentally deleted that branch

[oliviertassinari]

@aditya1906 Don't worry about it, we learn by doing things wrong :).

[aditya1906]

Thanks @oliviertassinari :-)