Add help to make file

[TerryHowe]

What this PR does / why we need it:
Add make help

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Please check the following list:

• Does the affected code have corresponding tests, e.g. unit test, E2E test?
• Does this change require a documentation update?
• Does this introduce breaking changes that would require an announcement or bumping the major version?
• Do all new files have an appropriate license header?

[codecov-commenter]

Codecov Report

Merging #975 (c7688bb) into main (7c09fd4) will not change coverage.
The diff coverage is n/a.

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@@           Coverage Diff           @@
##             main     #975   +/-   ##
=======================================
  Coverage   81.08%   81.08%           
=======================================
  Files          53       53           
  Lines        2776     2776           
=======================================
  Hits         2251     2251           
  Misses        356      356           
  Partials      169      169           

[sajayantony]

Should we make help the default target?
Looks nice -

❯ make help

Usage:
  make <target>
  test                                           build for linux amd64
  teste2e                                        run end to end tests
  covhtml                                        look at code coverage
  clean                                          clean up build
  build                                          build for all targets
  build-linux                                    build all linux architectures
  build-linux-amd64                              build for linux amd64
  build-linux-arm64                              build for linux arm64
  build-linux-arm-v7                             build for linux arm v7
  build-linux-s390x                              build for linux s390x
  build-mac                                      build all mac architectures
  build-mac-amd64                                build for mac amd64
  build-mac-arm64                                build for mac arm64
  build-windows                                  build all windows architectures
  build-windows-amd64                            build for windows amd64
  build-windows-arm64                            build for windows arm64
  check-encoding                                 check file CR/LF encoding
  fix-encoding                                   fix file CR/LF encoding
  tidy                                           go mod tidy
  vendor                                         go mod vendor
  fetch-dist                                     fetch distribution
  sign                                           sign
  teste2e-covdata                                test e2e coverage
  help                                           Display this help

[TerryHowe]

Should we make help the default target? Looks nice -

I fixed the help for the test target. To me, the ideal default target would build for the current OS/arch and run the tests. Either way though, I'd sooner do that as another PR.