Fix version badge on README.md -> v1.0.0-RC.1

[xellos00]

1. Type of change

Please delete options that are not relevant.

• New feature
• Enhancement
• Bug/fix (non-breaking change which fixes an issue)
• others (anything other than above)

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2. Summary

Please include a summary of the changes and which issue is fixed or solved.

Related: #475

Summary

Version & License badge should be

v1.0.0 & GPL-3.0

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3. Comments

Please, leave a comments if there's further action that requires.

 dongyookang DK 🐸   ~/ffplay/GolandProjects/xellos/vatz   ISSUE-475
 make coverage
fatal: No names found, cannot describe anything.
?       github.com/dsrvlabs/vatz        [no test files]
?       github.com/dsrvlabs/vatz/manager/types  [no test files]
?       github.com/dsrvlabs/vatz/mocks  [no test files]
ok      github.com/dsrvlabs/vatz/cmd    3.211s  coverage: 23.5% of statements
ok      github.com/dsrvlabs/vatz/manager/api    0.572s  coverage: 0.0% of statements [no tests to run]
ok      github.com/dsrvlabs/vatz/manager/config 0.456s  coverage: 77.8% of statements
ok      github.com/dsrvlabs/vatz/manager/dispatcher     0.836s  coverage: 7.1% of statements
ok      github.com/dsrvlabs/vatz/manager/executor       0.966s  coverage: 68.9% of statements
ok      github.com/dsrvlabs/vatz/manager/healthcheck    1.243s  coverage: 46.5% of statements
ok      github.com/dsrvlabs/vatz/manager/plugin 7.699s  coverage: 50.6% of statements
ok      github.com/dsrvlabs/vatz/monitoring/prometheus  1.094s  coverage: 0.0% of statements
ok      github.com/dsrvlabs/vatz/rpc    2.526s  coverage: 67.2% of statements
ok      github.com/dsrvlabs/vatz/utils  0.697s  coverage: 7.1% of statements
 dongyookang DK 🐸   ~/ffplay/GolandProjects/xellos/vatz   ISSUE-475

[meetrick]

LGTM

[gnongs]

LGTM!