`{{exprLast}}` and `{[exprRest}}` template placeholders

[zardoy]

closes https://github.com/ipatalas/vscode-postfix-ts/issues/90

Let me know what do you think. If its okay to add here I'll add tests.

[codecov[bot]]

Codecov Report

Base: 97.84% // Head: 97.31% // Decreases project coverage by -0.53% :warning:

Coverage data is based on head (03d2f85) compared to base (b83e0d2). Patch coverage: 82.35% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #91 +/- ## =========================================== - Coverage 97.84% 97.31% -0.54% =========================================== Files 21 21 Lines 1209 1228 +19 Branches 225 228 +3 =========================================== + Hits 1183 1195 +12 - Misses 25 32 +7 Partials 1 1 ``` | [Impacted Files](https://codecov.io/gh/ipatalas/vscode-postfix-ts/pull/91?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Ireneusz+Patalas) | Coverage Δ | | |---|---|---| | [src/completionItemBuilder.ts](https://codecov.io/gh/ipatalas/vscode-postfix-ts/pull/91/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Ireneusz+Patalas#diff-c3JjL2NvbXBsZXRpb25JdGVtQnVpbGRlci50cw==) | `91.80% <70.58%> (-4.60%)` | :arrow_down: | | [src/utils/infer-names.ts](https://codecov.io/gh/ipatalas/vscode-postfix-ts/pull/91/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Ireneusz+Patalas#diff-c3JjL3V0aWxzL2luZmVyLW5hbWVzLnRz) | `98.78% <94.11%> (-1.22%)` | :arrow_down: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Ireneusz+Patalas). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Ireneusz+Patalas)

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