adding decompress gzipped request middleware

[arun0009]

Adding decompress middleware that decompresses request if content-encoding is set to "gzip". We send in large amounts of data and we want to compress data on the network and decompress it in API. This is trivial for any API that ingests a large amount of payload. Also addresses one of the issues logged on echo #986.

Added tests as well to cover most of the scenarios. Can you please review @lammel

P.S Build was failing as github actions deprecated passing env variables, updated workflows/echo.yaml to fix this issue. More details here https://github.blog/changelog/2020-10-01-github-actions-deprecating-set-env-and-add-path-commands/

[codecov]

Codecov Report

Merging #1687 (b47042f) into master (7a90304) will increase coverage by 0.10%.
The diff coverage is 94.73%.

@@ Coverage Diff @@ ## master #1687 +/- ## ========================================== + Coverage 84.35% 84.45% +0.10%  ========================================== Files 28 29 +1 Lines 1911 1930 +19 ========================================== + Hits 1612 1630 +18  - Misses 189 190 +1  Partials 110 110 

Impacted Files	Coverage Δ
middleware/decompress.go	94.73% <94.73%> (ø)

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[lammel]

Looking good!

Would you mind adding a PR for this middleware with an example for the documentation in echox project?
That would definitely be helpful for all those backend REST API wrestlers our there having to transfer bigger payloads.

As the PR is already cleanup up, tests added and no breaking changes, will merge.

Thanks @arun0009 !