add license header lint check

[capri-xiyue]

TL;DR

add license header lint check

Detailed design

No response

Alternatives considered

No response

Additional information

No response

[sethvargo]

We do have a license check header, but it looks like it only runs on Go files:

pkg/.golangci.yml

Lines 133 to 152 in 8939fb6

	goheader:
	values:
	regexp:
	YEAR_AUTHOR: '\d{4} .*'
	INDENTATION: '[\t\f]+|[ ]{2,}'
	# default: ""
	template: |-
	Copyright {{ YEAR_AUTHOR }}
	Licensed under the Apache License, Version 2.0 (the "License");
	you may not use this file except in compliance with the License.
	You may obtain a copy of the License at
	{{ INDENTATION }}http://www.apache.org/licenses/LICENSE-2.0
	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	See the License for the specific language governing permissions and
	limitations under the License.