fix(codemirror): shift approach to remove placeholder

[danilowoz]

This shifts the approach used to replace the placeholder codebase to the CodeMirror editor. The previous implementation was using a React state which, for a moment, the editor didn't have any codebase at all. From now on, I brought back the previous implementation, which uses DOM API to remove the placeholder in the right moment of the CodeMirror is created, which is way faster than a React DOM flow.

[codesandbox-ci]

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Sandbox	Source
Sandpack Blog Example 1	Configuration

[github-actions]

Size changes

sandpack-react

Total base	Total current	+/-
819 kb	819 kb	⚠️ +37 bytes (+0.00%)

Details

Dependency name / file	Base	Current	+/-
index.js	21 kb	21 kb	⚠️ +37 bytes (+0.17%)
types.js	54 bytes	54 bytes	✅ 0 byte
@code-hike/classer	550 bytes	550 bytes	✅ 0 byte
@codemirror/closebrackets	54 kb	54 kb	✅ 0 byte
@codemirror/commands	62 kb	62 kb	✅ 0 byte
@codemirror/comment	12 kb	12 kb	✅ 0 byte
@codemirror/gutter	50 kb	50 kb	✅ 0 byte
@codemirror/highlight	59 kb	59 kb	✅ 0 byte
@codemirror/history	50 kb	50 kb	✅ 0 byte
@codemirror/lang-css	71 kb	71 kb	✅ 0 byte
@codemirror/lang-html	110 kb	110 kb	✅ 0 byte
@codemirror/lang-javascript	92 kb	92 kb	✅ 0 byte
@codemirror/language	58 kb	58 kb	✅ 0 byte
@codemirror/matchbrackets	54 kb	54 kb	✅ 0 byte
@codemirror/state	12 kb	12 kb	✅ 0 byte
@codemirror/view	54 kb	54 kb	✅ 0 byte
@codesandbox/sandpack-client	7 kb	7 kb	✅ 0 byte
@react-hook/intersection-observer	4 kb	4 kb	✅ 0 byte
codesandbox-import-utils	128 bytes	128 bytes	✅ 0 byte
react-devtools-inline	49 kb	49 kb	✅ 0 byte
react-is	824 bytes	824 bytes	✅ 0 byte

sandpack-client

Total base	Total current	+/-
10 kb	10 kb	✅ 0 byte

Details

Dependency name / file	Base	Current	+/-
client.js	4 kb	4 kb	✅ 0 byte
file-resolver-protocol.js	777 bytes	777 bytes	✅ 0 byte
iframe-protocol.js	623 bytes	623 bytes	✅ 0 byte
index.js	4 kb	4 kb	✅ 0 byte
types.js	54 bytes	54 bytes	✅ 0 byte
utils.js	1 kb	1 kb	✅ 0 byte