Tell us about your environment

• ESLint version: 5.9.0
• eslint-plugin-vue version: 3.2.1
• Node version: 10.14.1

Please show your full configuration:

{
 "name": "test",
 "version": "0.1.0",
 "private": true,
 "scripts": {
 "serve": "vue-cli-service serve",
 "build": "vue-cli-service build",
 "lint": "vue-cli-service lint"
 },
 "dependencies": {
 "vue": "^2.5.17"
 },
 "devDependencies": {
 "@vue/cli-plugin-babel": "^3.2.0",
 "@vue/cli-plugin-eslint": "^3.2.0",
 "@vue/cli-service": "^3.2.0",
 "babel-eslint": "^10.0.1",
 "eslint": "^5.8.0",
 "eslint-plugin-vue": "^5.0.0-0",
 "vue-template-compiler": "^2.5.17"
 },
 "eslintConfig": {
 "root": true,
 "env": {
 "node": true
 },
 "extends": [
 "plugin:vue/recommended",
 "eslint:recommended"
 ],
 "parserOptions": {
 "parser": "babel-eslint"
 }
 },
 "postcss": {
 "plugins": {
 "autoprefixer": {}
 }
 },
 "browserslist": [
 "> 1%",
 "last 2 versions",
 "not ie <= 8"
 ]
}

What did you do?

1. Create a new project in vue ui with default template;
2. In vue ui open Configuration -> ESLint configuration -> Rules tab + select Error for vue/component-name-in-template-casing + Save settings;
3. Open App.vue and add, for example <b-button>My Button</b-button>. Save changes;
4. npm run lint;
5. Open App.vue again and you will see, that b-button is changes to BButton, because of the rule to transform components to PascalCase. I checked that bootstrap-vue works in camelCase (bButton) and kebab-case (b-button), but not in PascalCase (BButton), probably because in the first part of b-button/BButton there is just 1 letter (I can guess, should be at least 2 instead).

What did you expect to happen?
So, as a result, as I understand, the rule vue/component-name-in-template-casing should not transform component name in case, if the first part of <b-button> has just one letter or if the first letter has lower case + the 2nd letter has upper case + the 3rd letter has lower case (bButton).

What actually happened?
<b-button> and <bButton> are transformed to <BButton>.

Additional info
Same problem happens with Vuetify (commented in #397)