fix(parser): JavaScript files are not all interpreted as a Vue component anymore

[Kocal]

Close #136

Since #128, every JavaScripts files were seen as Vue component.
Now, .js files should at least have one @vue tag in a comment to be considered as a Vue component.

Recognized as a Vue component:

// Component.js

/**
 * @vue
 */
export default {
  name: 'Component',
}

Not recognized as a Vue component:

// File.js

export default {
  name: 'File',
}

[codecov-io]

Codecov Report

Merging #137 into master will decrease coverage by 23.61%.
The diff coverage is 0%.

@@             Coverage Diff             @@
##           master     #137       +/-   ##
===========================================
- Coverage   94.44%   70.83%   -23.62%     
===========================================
  Files           4        5        +1     
  Lines          36       48       +12     
  Branches        8       11        +3     
===========================================
  Hits           34       34               
- Misses          2       11        +9     
- Partials        0        3        +3

Impacted Files	Coverage Δ
lib/core/issers.js	0% <0%> (ø)

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