Add "mission and values" page

[ocfnash]

No description provided.

[chrisflav]

Could you elaborate a bit on how these "missions and values" were drafted? Is this the consensus of the maintainer team or is this your personal suggestion?

[grunweg]

This was discussed in the maintainers stream, received broad support (and some feedback) there and no objections. I wouldn't call this a done decision, though: feedback is still welcome.

[chrisflav]

The first version contained a "mission statement", which I was (independent of its content) quite surprised by to see without any context. The new version, which only contains the values is much less controversial I think.

[chrisflav]

I can't make inline comments at the moment because of the github issue, so let me write some thoughts here:

• In the introductory paragraph for "Implications for PR review" I would link to the review guide. Generally, there is quite a bit of overlap here. Maybe you can comment on what the main purpose of this section is? Is it "give a summary of our review process to outsiders, in particular non-formalists"?
• I would put the "Are the definitions correct" paragraph much higher, maybe after "Is the author a human".
• "instance diamonds": It seems to me that the target audience of this text includes non-formalisers. For them, the term "diamond" will not be known. There are also some other technical terms like set_option maxHeartbeats etc.