Create Overview proposal decision (#132)

* Create Overview proposal decision

Create the proposal decision for the proposal in PR83: An incomplete, early, and in-progress overview of the language design

* Update proposals/p0083-decision.md

Co-authored-by: Jon Meow <46229924+jonmeow@users.noreply.github.com>

* Rerun pre-commit

Adjusted some spaces.

* Rename decision to use _ instead of -

Co-authored-by: Jon Meow <46229924+jonmeow@users.noreply.github.com>

proposals/p0083_decision.md

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+# Decision for: An incomplete, early, and in-progress overview of the language design
+
+<!--
+Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+Exceptions. See /LICENSE for license information.
+SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+-->
+
+Proposal accepted on 2020-07-28
+
+Affirming:
+
+-   [austern](https://github.com/austern)
+-   [chandlerc](https://github.com/chandlerc)
+-   [geoffromer](https://github.com/geoffromer)
+-   [gribozavr](https://github.com/gribozavr)
+-   [josh11b](https://github.com/josh11b)
+-   [tituswinters](https://github.com/tituswinters)
+-   [zygoloid](https://github.com/zygoloid)
+
+Abstaining:
+
+-   [noncombatant](https://github.com/noncombatant)
+
+## Open questions
+
+There were no open questions.
+
+## Rationale
+
+This proposal provides some much-needed context for a lot of our discussions and
+deliberations about Carbon. Having a skeleton in place for the language design
+is an important step forward. We can't make language design decisions in a
+vacuum -- we need a "blurry outline" of the big picture before we can start
+filling in the details of any particular area. We need to establish a common
+frame of reference regarding the overall shape of the language, so that we can
+parallelize the in-depth design work.
+
+That means that, by necessity, this proposal suggests lots of concrete design
+decisions that have not yet had sufficient analysis for us to affirm them. There
+is a shared understanding that we are not committing to any of those decisions,
+only to the broad picture painted by the combination of those decisions, and
+that all such decisions need to be revisited by another proposal before we
+consider them to be agreed on. There is a substantial risk of anchoring how we
+think about Carbon -- we’ll just have to do our best to avoid taking this doc as
+a given when evaluating subsequent proposals. Those propopsals must justify a
+direction that agrees with this doc as much as one that does not agree with it.
+
+This doc sets the stage for increasingly incremental steps towards a complete
+design. Establishing a structure for the design is especially helpful as it will
+show how things do or do not connect across the language.
+
+Adopting this largely work-in-progress overview in order to see the structure of
+things, while still needing to resolve the specifics in each area, will directly
+help reinforce our goal of language evolution over time. This will help us learn
+how to effectively iterate, and how to compensate and overcome the risks of
+anchoring, change aversion, and other challenges.