docs: add adr template (#338)

* add docs section and adr template

* change cosmos-sdk to bridge

docs/architecture/README.md

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+# Architecture Decision Records (ADR)
+
+This is a location to record all high-level architecture decisions For the Gravity Bridge.
+
+An Architectural Decision (**AD**) is a software design choice that addresses a functional or non-functional requirement that is architecturally significant.
+An Architecturally Significant Requirement (**ASR**) is a requirement that has a measurable effect on a software system’s architecture and quality.
+An Architectural Decision Record (**ADR**) captures a single AD, such as often done when writing personal notes or meeting minutes; the collection of ADRs created and maintained in a project constitute its decision log. All these are within the topic of Architectural Knowledge Management (AKM).
+
+You can read more about the ADR concept in this [blog post](https://product.reverb.com/documenting-architecture-decisions-the-reverb-way-a3563bb24bd0#.78xhdix6t).
+
+## Rationale
+
+ADRs are intended to be the primary mechanism for proposing new feature designs and new processes, for collecting community input on an issue, and for documenting the design decisions.
+An ADR should provide:
+
+- Context on the relevant goals and the current state
+- Proposed changes to achieve the goals
+- Summary of pros and cons
+- References
+- Changelog
+
+Note the distinction between an ADR and a spec. The ADR provides the context, intuition, reasoning, and
+justification for a change in architecture, or for the architecture of something
+new. The spec is much more compressed and streamlined summary of everything as
+it stands today.
+
+If recorded decisions turned out to be lacking, convene a discussion, record the new decisions here, and then modify the code to match.
+
+## ADR Table of Contents
+
+### Accepted
+
+### Proposed

docs/architecture/adr-template.md

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+# ADR {ADR-NUMBER}: {TITLE}
+
+## Changelog
+
+- {date}: {changelog}
+
+## Status
+
+{DRAFT | PROPOSED} Not Implemented
+
+> Please have a look at the [PROCESS](./PROCESS.md#adr-status) page.
+> Use DRAFT if the ADR is in a draft stage (draft PR) or PROPOSED if it's in review.
+
+## Abstract
+
+> "If you can't explain it simply, you don't understand it well enough." Provide a simplified and layman-accessible explanation of the ADR.
+> A short (~200 word) description of the issue being addressed.
+
+## Context
+
+> This section describes the forces at play, including technological, political, social, and project local. These forces are probably in tension, and should be called out as such. The language in this section is value-neutral. It is simply describing facts. It should clearly explain the problem and motivation that the proposal aims to resolve.
+> {context body}
+
+## Decision
+
+> This section describes our response to these forces. It is stated in full sentences, with active voice. "We will ..."
+> {decision body}
+
+## Consequences
+
+> This section describes the resulting context, after applying the decision. All consequences should be listed here, not just the "positive" ones. A particular decision may have positive, negative, and neutral consequences, but all of them affect the team and project in the future.
+
+### Backwards Compatibility
+
+> All ADRs that introduce backwards incompatibilities must include a section describing these incompatibilities and their severity. The ADR must explain how the author proposes to deal with these incompatibilities. ADR submissions without a sufficient backwards compatibility treatise may be rejected outright.
+
+### Positive
+
+{positive consequences}
+
+### Negative
+
+{negative consequences}
+
+### Neutral
+
+{neutral consequences}
+
+## Further Discussions
+
+While an ADR is in the DRAFT or PROPOSED stage, this section should contain a summary of issues to be solved in future iterations (usually referencing comments from a pull-request discussion).
+Later, this section can optionally list ideas or improvements the author or reviewers found during the analysis of this ADR.
+
+## Test Cases [optional]
+
+Test cases for an implementation are mandatory for ADRs that are affecting consensus changes. Other ADRs can choose to include links to test cases if applicable.
+
+## References
+
+- {reference link}