improve diff view of long string values

[cppforlife]

it would be pretty awesome to improve how we show diff for long string values, especially when they are wrapped in the terminal. for example

--- update configmap/linkerd-config (v1) namespace: linkerd
  ...
  2,  2     global: |
  3     -     {"linkerdNamespace":"linkerd","cniEnabled":false,"version":"stable-2.3.2","identityContext":{"trustDomain":"cluster.local","trustAnchorsPem":"-----BEGIN CERTIFICATE-----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\n6iLVXPjv\n-----END CERTIFICATE-----\n","issuanceLifetime":"86400s","clockSkewAllowance":"20s"},"autoInjectContext":null}
      3 +     {"linkerdNamespace":"linkerd","cniEnabled":false,"version":"stable-2.3.2","identityContext":{"trustDomain":"cluster.local","trustAnchorsPem":"-----BEGIN CERTIFICATE-----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\n6iLVXPjv\n-----END CERTIFICATE-----\n","issuanceLifetime":"86400s","clockSkewAllowance":"20s"},"autoInjectContext":{}}
  4,  4     install: |
  5     -     {"uuid":"a3d53c7f-04cd-4110-85c1-2852e3d795c1","cliVersion":"stable-2.3.2","flags":[]}
      5 +     {"uuid":"a3d53c7f-04cd-4110-85c1-2852e3d795c1","cliVersion":"stable-2.3.2","flags":[{"name":"proxy-auto-inject","value":"true"}]}

[renuy]

Option1: use a darker green or red to highlight the diff. #109