[blockscout] apply celo theme bis (2)

[jcortejoso]

Replaces #9

Motivation

Re-brand blockscout to celo theme - fixes celo-org/celo-monorepo#997 and celo-org/celo-monorepo#994

Enhancements

Upgrading

prerequisite: #8
once that PR is merged - this PR can point to celo-org/blockscout:master

Env vars

export NETWORK=Celo
export NETWORK_ID=11001
export SUBNETWORK=<"Celo Integration" | "Celo Alfajores" | ...>
export ETHEREUM_JSONRPC_VARIANT=geth
export ETHEREUM_JSONRPC_HTTP_URL=http://localhost:8545
export ETHEREUM_JSONRPC_TRACE_URL=http://localhost:8545
export ETHEREUM_JSONRPC_WS_URL=ws://localhost:8546
export COIN=cGLD
export WS_SECRET=<WS_SECRET>
export POSTGRES_PASSWORD=<POSTGRES_SECRET>
export LOGO=/images/celo_logo.svg

Why should we merge these changes. If using GitHub keywords to close issues, this is optional as the motivation can be read on the issue page.

Changelog

Enhancements

Things you added that don't break anything. Regression tests for Bug Fixes count as Enhancements.

Bug Fixes

Things you changed that fix bugs. If a fixes a bug, but in so doing adds a new requirement, removes code, or requires a database reset and reindex, the breaking part of the change should be added to Incompatible Changes below also.

Incompatible Changes

Things you broke while doing Enhancements and Bug Fixes. Breaking changes include (1) adding new requirements and (2) removing code. Renaming counts as (2) because a rename is a removal followed by an add.

Upgrading

If you have any Incompatible Changes in the above Changelog, outline how users of prior versions can upgrade once this PR lands or when reviewers are testing locally. A common upgrading step is "Database reset and re-index required".